diff --git a/firmware/application/apps/ais_app.cpp b/firmware/application/apps/ais_app.cpp
index 07f2045cb..093d65716 100644
--- a/firmware/application/apps/ais_app.cpp
+++ b/firmware/application/apps/ais_app.cpp
@@ -456,7 +456,10 @@ void AISAppView::on_tick_second() {
     ++timer_seconds;
     if (timer_seconds % 10 == 0) {
         if (recent_entry_detail_view.hidden()) return;
-        recent_entry_detail_view.update_map_markers(recent);
+        if (got_new_packet) {
+            got_new_packet = false;
+            recent_entry_detail_view.update_map_markers(recent);
+        }
     }
 }
 
@@ -475,7 +478,7 @@ void AISAppView::on_packet(const ais::Packet& packet) {
     if (logger) {
         logger->on_packet(packet);
     }
-
+    got_new_packet = true;
     auto& entry = ::on_packet(recent, packet.source_id());
     entry.update(packet);
     recent_entries_view.set_dirty();
diff --git a/firmware/application/apps/ais_app.hpp b/firmware/application/apps/ais_app.hpp
index 20bb3a67c..094d1b37a 100644
--- a/firmware/application/apps/ais_app.hpp
+++ b/firmware/application/apps/ais_app.hpp
@@ -221,6 +221,7 @@ class AISAppView : public View {
     };
     SignalToken signal_token_tick_second{};
     uint8_t timer_seconds = 0;
+    bool got_new_packet{false};  // got any new packet since latest screen update?
 
     MessageHandlerRegistration message_handler_packet{
         Message::ID::AISPacket,
diff --git a/firmware/application/apps/ui_adsb_rx.cpp b/firmware/application/apps/ui_adsb_rx.cpp
index 83a60eedc..c0f9fd4c1 100644
--- a/firmware/application/apps/ui_adsb_rx.cpp
+++ b/firmware/application/apps/ui_adsb_rx.cpp
@@ -635,14 +635,14 @@ void ADSBRxView::refresh_ui() {
 
         if (details_view->map_active()) {
             // Is it time to clear and refresh the map's markers?
-            if (ticks_since_marker_refresh >= MARKER_UPDATE_SECONDS) {
+            if (ticks_since_marker_refresh >= (details_view->get_map_type() == MAP_TYPE_OSM ? MARKER_UPDATE_SECONDS_OSM : MARKER_UPDATE_SECONDS_BIN)) {
                 map_needs_update = true;
                 ticks_since_marker_refresh = 0;
                 details_view->clear_map_markers();
             }
         } else {
             // Refresh map immediately once active.
-            ticks_since_marker_refresh = MARKER_UPDATE_SECONDS;
+            ticks_since_marker_refresh = MARKER_UPDATE_SECONDS_OSM;  // this is the bigger, so set it to force
         }
 
         // Process the entries list.
diff --git a/firmware/application/apps/ui_adsb_rx.hpp b/firmware/application/apps/ui_adsb_rx.hpp
index 039135f5d..66f2cfbbc 100644
--- a/firmware/application/apps/ui_adsb_rx.hpp
+++ b/firmware/application/apps/ui_adsb_rx.hpp
@@ -64,8 +64,9 @@ namespace ui {
 #define VEL_AIR_SUBSONIC 3
 #define VEL_AIR_SUPERSONIC 4
 
-#define O_E_FRAME_TIMEOUT 20     // timeout between odd and even frames
-#define MARKER_UPDATE_SECONDS 5  // "other" map marker redraw interval
+#define O_E_FRAME_TIMEOUT 20          // timeout between odd and even frames
+#define MARKER_UPDATE_SECONDS_OSM 10  // "other" map marker redraw interval for osm
+#define MARKER_UPDATE_SECONDS_BIN 5   // "other" map marker redraw interval for bin map
 
 /* Thresholds (in seconds) that define the transition between ages. */
 struct ADSBAgeLimit {
@@ -277,6 +278,13 @@ class ADSBRxDetailsView : public View {
 
     std::string title() const override { return "Details"; }
 
+    MapType get_map_type() {
+        if (geomap_view_)
+            return geomap_view_->get_map_type();
+        else
+            return MapType::MAP_TYPE_BIN;  // default
+    }
+
    private:
     void refresh_ui();
     void on_gps(const GPSPosDataMessage* msg);
@@ -388,7 +396,7 @@ class ADSBRxView : public View {
 
     SignalToken signal_token_tick_second{};
     uint8_t tick_count = 0;
-    uint16_t ticks_since_marker_refresh{MARKER_UPDATE_SECONDS};
+    uint16_t ticks_since_marker_refresh{MARKER_UPDATE_SECONDS_OSM};
 
     /* Max number of entries that can be updated in a single pass.
      * 16 is one screen of recent entries. */
diff --git a/firmware/application/external/calculator/ivt.hpp b/firmware/application/external/calculator/ivt.hpp
index 8259c369a..bcf49f072 100644
--- a/firmware/application/external/calculator/ivt.hpp
+++ b/firmware/application/external/calculator/ivt.hpp
@@ -440,7 +440,7 @@ static void _sumlr(void);
 #undef __O
 #undef __P
 
-#define PI 3.141592653589793
+#include "mathdef.hpp"
 
 static void _numinput(byte k);
 static double dpush(double d);
diff --git a/firmware/application/external/doom/ui_doom.cpp b/firmware/application/external/doom/ui_doom.cpp
index dc63b60a8..a49f413b4 100644
--- a/firmware/application/external/doom/ui_doom.cpp
+++ b/firmware/application/external/doom/ui_doom.cpp
@@ -31,7 +31,7 @@ int HALF_HEIGHT = 0;
 #define JOGGING_SPEED 1.2
 #define MAX_ENTITY_DISTANCE 200
 #define ITEM_COLLIDER_DIST 6
-#define PI 3.14159265358979323846
+#include "mathdef.hpp"
 #define GUN_WIDTH 30
 #define GUN_HEIGHT 40
 #define GUN_TARGET_POS 24
diff --git a/firmware/application/external/wardrivemap/ui_wardrivemap.cpp b/firmware/application/external/wardrivemap/ui_wardrivemap.cpp
index 21f5d73a2..5001fec1a 100644
--- a/firmware/application/external/wardrivemap/ui_wardrivemap.cpp
+++ b/firmware/application/external/wardrivemap/ui_wardrivemap.cpp
@@ -158,9 +158,10 @@ WardriveMapView::WardriveMapView(NavigationView& nav)
     }
 
     // never move this before the first load() bc that will mess load up
-    geomap.on_move = [this](float lon, float lat) {
+    geomap.on_move = [this](float lon, float lat, bool absolute) {
         (void)lon;
         (void)lat;
+        (void)absolute;
         load_markers();
     };
     btn_back.on_select = [this, &nav](Button&) {
diff --git a/firmware/application/file.cpp b/firmware/application/file.cpp
index 6da93056e..df0f22849 100644
--- a/firmware/application/file.cpp
+++ b/firmware/application/file.cpp
@@ -113,7 +113,7 @@ File::Result<bool> File::eof() {
 File::Result<File::Offset> File::seek(Offset new_position) {
     /* NOTE: Returns *old* position, not new position */
     const auto old_position = tell();
-    const auto result = f_lseek(&f, new_position);
+    const auto result = (old_position == new_position) ? FR_OK : f_lseek(&f, new_position);
     if (result != FR_OK) {
         return {static_cast<Error>(result)};
     }
diff --git a/firmware/application/ui/ui_geomap.cpp b/firmware/application/ui/ui_geomap.cpp
index 83defae98..8e3ca5cd7 100644
--- a/firmware/application/ui/ui_geomap.cpp
+++ b/firmware/application/ui/ui_geomap.cpp
@@ -22,21 +22,17 @@
  */
 
 #include "ui_geomap.hpp"
-
 #include "portapack.hpp"
-
 #include <cstring>
 #include <stdio.h>
-
+#include <string_view>
 using namespace portapack;
-
 #include "string_format.hpp"
 #include "complex.hpp"
 #include "ui_font_fixed_5x8.hpp"
 #include "file_path.hpp"
 
 namespace ui {
-
 GeoPos::GeoPos(
     const Point pos,
     const alt_unit altitude_unit,
@@ -188,6 +184,7 @@ int32_t GeoPos::speed() {
 GeoMap::GeoMap(
     Rect parent_rect)
     : Widget{parent_rect}, markerListLen(0) {
+    has_osm = use_osm = find_osm_file_tile();
 }
 
 bool GeoMap::on_encoder(const EncoderEvent delta) {
@@ -201,6 +198,8 @@ bool GeoMap::on_encoder(const EncoderEvent delta) {
                 map_zoom += (map_zoom >= MAP_ZOOM_RESOLUTION_LIMIT) ? map_zoom : 1;
             }
         }
+        map_osm_zoom++;
+        if (has_osm) set_osm_max_zoom();
     } else if (delta < 0) {
         if (map_zoom > -MAX_MAP_ZOOM_OUT) {
             if (map_zoom == 1) {
@@ -212,12 +211,18 @@ bool GeoMap::on_encoder(const EncoderEvent delta) {
                     map_zoom--;
             }
         }
+        if (map_osm_zoom > 0) map_osm_zoom--;
     } else {
         return false;
     }
 
     map_visible = map_opened && (map_zoom <= MAP_ZOOM_RESOLUTION_LIMIT);
-    zoom_pixel_offset = (map_visible && (map_zoom > 1)) ? (float)map_zoom / 2 : 0.0f;
+    if (use_osm) {
+        map_visible = true;
+        zoom_pixel_offset = 0;
+    } else {
+        zoom_pixel_offset = (map_visible && (map_zoom > 1)) ? (float)map_zoom / 2 : 0.0f;
+    }
 
     // Trigger map redraw
     redraw_map = true;
@@ -225,7 +230,7 @@ bool GeoMap::on_encoder(const EncoderEvent delta) {
     return true;
 }
 
-void GeoMap::map_read_line(ui::Color* buffer, uint16_t pixels) {
+void GeoMap::map_read_line_bin(ui::Color* buffer, uint16_t pixels) {
     if (map_zoom == 1) {
         map_file.read(buffer, pixels << 1);
     } else if (map_zoom > 1) {
@@ -264,39 +269,86 @@ void GeoMap::draw_markers(Painter& painter) {
 void GeoMap::draw_marker_item(Painter& painter, GeoMarker& item, const Color color, const Color fontColor, const Color backColor) {
     const auto r = screen_rect();
     const ui::Point itemPoint = item_rect_pixel(item);
-
     if ((itemPoint.x() >= 0) && (itemPoint.x() < r.width()) &&
         (itemPoint.y() > 10) && (itemPoint.y() < r.height()))  // Dont draw within symbol size of top
     {
-        draw_marker(painter, {itemPoint.x(), itemPoint.y() + r.top()}, item.angle, item.tag, color, fontColor, backColor);
+        draw_marker(painter, {itemPoint.x() + r.left(), itemPoint.y() + r.top()}, item.angle, item.tag, color, fontColor, backColor);
     }
 }
 
 // Calculate screen position of item, adjusted for zoom factor.
 ui::Point GeoMap::item_rect_pixel(GeoMarker& item) {
-    const auto r = screen_rect();
-    const auto geomap_rect_half_width = r.width() / 2;
-    const auto geomap_rect_half_height = r.height() / 2;
-
-    GeoPoint mapPoint = lat_lon_to_map_pixel(item.lat, item.lon);
-    float x = mapPoint.x - x_pos;
-    float y = mapPoint.y - y_pos;
-
-    if (map_zoom > 1) {
-        x = x * map_zoom + zoom_pixel_offset;
-        y = y * map_zoom + zoom_pixel_offset;
-    } else if (map_zoom < 0) {
-        x = x / (-map_zoom);
-        y = y / (-map_zoom);
+    if (!use_osm) {
+        const auto r = screen_rect();
+        const auto geomap_rect_half_width = r.width() / 2;
+        const auto geomap_rect_half_height = r.height() / 2;
+        GeoPoint mapPoint = lat_lon_to_map_pixel(item.lat, item.lon);
+        float x = mapPoint.x - x_pos;
+        float y = mapPoint.y - y_pos;
+        if (map_zoom > 1) {
+            x = x * map_zoom + zoom_pixel_offset;
+            y = y * map_zoom + zoom_pixel_offset;
+        } else if (map_zoom < 0) {
+            x = x / (-map_zoom);
+            y = y / (-map_zoom);
+        }
+        x += geomap_rect_half_width;
+        y += geomap_rect_half_height;
+        return {(int16_t)x, (int16_t)y};
     }
-
-    x += geomap_rect_half_width;
-    y += geomap_rect_half_height;
-
+    // osm calculation
+    double y = lat_to_pixel_y_tile(item.lat, map_osm_zoom) - viewport_top_left_py;
+    double x = lon_to_pixel_x_tile(item.lon, map_osm_zoom) - viewport_top_left_px;
     return {(int16_t)x, (int16_t)y};
 }
 
-// Converts latitude/longitude to pixel coordinates in map file.
+/**
+ * @brief Converts longitude to a map tile's X-coordinate.
+ * @param lon The longitude in degrees.
+ * @param zoom The zoom level.
+ * @return The X-coordinate of the tile.
+ */
+int GeoMap::lon2tile(double lon, int zoom) {
+    return (int)floor((lon + 180.0) / 360.0 * pow(2.0, zoom));
+}
+
+/**
+ * @brief Converts latitude to a map tile's Y-coordinate.
+ * @param lat The latitude in degrees.
+ * @param zoom The zoom level.
+ * @return The Y-coordinate of the tile.
+ */
+int GeoMap::lat2tile(double lat, int zoom) {
+    // Convert latitude from degrees to radians for trigonometric functions
+    double lat_rad = lat * M_PI / 180.0;
+    // Perform the Mercator projection calculation
+    return (int)floor((1.0 - log(tan(lat_rad) + 1.0 / cos(lat_rad)) / M_PI) / 2.0 * pow(2.0, zoom));
+}
+
+void GeoMap::set_osm_max_zoom() {
+    if (map_osm_zoom > 20) map_osm_zoom = 20;
+    for (uint8_t i = map_osm_zoom; i > 0; i--) {
+        int tile_x = lon2tile(lon_, i);
+        int tile_y = lat2tile(lat_, i);
+        std::string filename = "/OSM/" + to_string_dec_int(i) + "/" + to_string_dec_int(tile_x) + "/" + to_string_dec_int(tile_y) + ".bmp";
+        std::filesystem::path file_path(filename);
+        if (file_exists(file_path)) {
+            map_osm_zoom = i;
+            return;
+        }
+    }
+    map_osm_zoom = 0;  // should not happen
+}
+
+// checks if the tile file presents or not. to determine if we got osm or not
+uint8_t GeoMap::find_osm_file_tile() {
+    std::string filename = "/OSM/" + to_string_dec_int(0) + "/" + to_string_dec_int(0) + "/" + to_string_dec_int(0) + ".bmp";
+    std::filesystem::path file_path(filename);
+    if (file_exists(file_path)) return 1;
+    return 0;  // not found
+}
+
+// Converts latitude/longitude to pixel coordinates in binary map file.
 // (Note that when map_zoom==1, one pixel in map file corresponds to 1 pixel on screen)
 GeoPoint GeoMap::lat_lon_to_map_pixel(float lat, float lon) {
     // Using WGS 84/Pseudo-Mercator projection
@@ -310,9 +362,7 @@ GeoPoint GeoMap::lat_lon_to_map_pixel(float lat, float lon) {
 }
 
 // Draw grid in place of map (when zoom-in level is too high).
-void GeoMap::draw_map_grid() {
-    const auto r = screen_rect();
-
+void GeoMap::draw_map_grid(ui::Rect r) {
     // Grid spacing is just based on zoom at the moment, and centered on screen.
     // TODO: Maybe align with latitude/longitude seconds instead?
     int grid_spacing = map_zoom * 2;
@@ -332,60 +382,184 @@ void GeoMap::draw_map_grid() {
     }
 }
 
+double GeoMap::tile_pixel_x_to_lon(int x, int zoom) {
+    double map_width = pow(2.0, zoom) * TILE_SIZE;
+    return (x / map_width * 360.0) - 180.0;
+}
+
+double GeoMap::tile_pixel_y_to_lat(int y, int zoom) {
+    double map_height = pow(2.0, zoom) * TILE_SIZE;
+    double n = M_PI * (1.0 - 2.0 * y / map_height);
+    return atan(sinh(n)) * 180.0 / M_PI;
+}
+
+double GeoMap::lon_to_pixel_x_tile(double lon, int zoom) {
+    return ((lon + 180.0) / 360.0) * pow(2.0, zoom) * TILE_SIZE;
+}
+
+double GeoMap::lat_to_pixel_y_tile(double lat, int zoom) {
+    double lat_rad = lat * M_PI / 180.0;
+    double sin_lat = sin(lat_rad);
+    return ((1.0 - log((1.0 + sin_lat) / (1.0 - sin_lat)) / (2.0 * M_PI)) / 2.0) * pow(2.0, zoom) * TILE_SIZE;
+}
+
+bool GeoMap::draw_osm_file(int zoom, int tile_x, int tile_y, int relative_x, int relative_y) {
+    const auto r = screen_rect();
+    // Early exit if the tile is completely outside the viewport
+    if (relative_x >= r.width() || relative_y >= r.height() ||
+        relative_x + TILE_SIZE <= 0 || relative_y + TILE_SIZE <= 0) {
+        return true;
+    }
+
+    BMPFile bmp{};
+    bmp.open("/OSM/" + to_string_dec_int(zoom) + "/" + to_string_dec_int(tile_x) + "/" + to_string_dec_int(tile_y) + ".bmp", true);
+    // 1. Define the source and destination areas, starting with the full tile.
+    int src_x = 0;
+    int src_y = 0;
+    int dest_x = relative_x;
+    int dest_y = relative_y;
+    int clip_w = TILE_SIZE;
+    int clip_h = TILE_SIZE;
+    // 2. Clip left edge
+    if (dest_x < 0) {
+        src_x = -dest_x;
+        clip_w += dest_x;
+        dest_x = 0;
+    }
+    // 3. Clip top edge
+    if (dest_y < 0) {
+        src_y = -dest_y;
+        clip_h += dest_y;
+        dest_y = 0;
+    }
+    // 4. Clip right edge
+    if (dest_x + clip_w > r.width()) {
+        clip_w = r.width() - dest_x;
+    }
+    // 5. Clip bottom edge
+    if (dest_y + clip_h > r.height()) {
+        clip_h = r.height() - dest_y;
+    }
+    // 6. If clipping resulted in no visible area, we're done.
+    if (clip_w <= 0 || clip_h <= 0) {
+        return true;
+    }
+
+    if (!bmp.is_loaded()) {
+        // Draw an error rectangle using the calculated clipped dimensions
+        ui::Rect error_rect{{dest_x + r.left(), dest_y + r.top()}, {clip_w, clip_h}};
+        display.fill_rectangle(error_rect, Theme::getInstance()->bg_darkest->background);
+        return false;
+    }
+    std::vector<ui::Color> line(clip_w);
+    for (int y = 0; y < clip_h; ++y) {
+        int source_row = src_y + y;
+        int dest_row = dest_y + y;
+        bmp.seek(src_x, source_row);
+        for (int x = 0; x < clip_w; ++x) {
+            bmp.read_next_px(line[x], true);
+        }
+        display.draw_pixels({dest_x + r.left(), dest_row + r.top(), clip_w, 1}, line);
+    }
+    return true;
+}
+
 void GeoMap::paint(Painter& painter) {
     const auto r = screen_rect();
     std::array<ui::Color, geomap_rect_width> map_line_buffer;
     int16_t zoom_seek_x, zoom_seek_y;
 
-    // Ony redraw map if it moved by at least 1 pixel or the markers list was updated
-    if (map_zoom <= 1) {
-        // Zooming out, or no zoom
-        const int min_diff = abs(map_zoom);
-        if ((int)abs(x_pos - prev_x_pos) >= min_diff)
-            redraw_map = true;
-        else if ((int)abs(y_pos - prev_y_pos) >= min_diff)
-            redraw_map = true;
+    if (!use_osm) {
+        // Ony redraw map if it moved by at least 1 pixel or the markers list was updated
+        if (map_zoom <= 1) {
+            // Zooming out, or no zoom
+            const int min_diff = abs(map_zoom);
+            if ((int)abs(x_pos - prev_x_pos) >= min_diff)
+                redraw_map = true;
+            else if ((int)abs(y_pos - prev_y_pos) >= min_diff)
+                redraw_map = true;
+        } else {
+            // Zooming in; magnify position differences (utilizing zoom_pixel_offset)
+            if ((int)(abs(x_pos - prev_x_pos) * map_zoom) >= 1)
+                redraw_map = true;
+            else if ((int)(abs(y_pos - prev_y_pos) * map_zoom) >= 1)
+                redraw_map = true;
+        }
     } else {
-        // Zooming in; magnify position differences (utilizing zoom_pixel_offset)
-        if ((int)(abs(x_pos - prev_x_pos) * map_zoom) >= 1)
-            redraw_map = true;
-        else if ((int)(abs(y_pos - prev_y_pos) * map_zoom) >= 1)
-            redraw_map = true;
+        // using osm; needs to be stricter with the redraws, it'll be checked on move
     }
 
     if (redraw_map) {
-        prev_x_pos = x_pos;  // Note x_pos/y_pos pixel position in map file now correspond to screen rect CENTER pixel
-        prev_y_pos = y_pos;
         redraw_map = false;
-
-        // Adjust starting corner position of map per zoom setting;
-        // When zooming in the map should technically by shifted left & up by another map_zoom/2 pixels but
-        // the map_read_line() function doesn't handle that yet so we're adjusting markers instead (see zoom_pixel_offset).
-        if (map_zoom > 1) {
-            zoom_seek_x = x_pos - (float)r.width() / (2 * map_zoom);
-            zoom_seek_y = y_pos - (float)r.height() / (2 * map_zoom);
-        } else {
-            zoom_seek_x = x_pos - (r.width() * abs(map_zoom)) / 2;
-            zoom_seek_y = y_pos - (r.height() * abs(map_zoom)) / 2;
-        }
-
         if (map_visible) {
-            // Read from map file and display to zoomed scale
-            int duplicate_lines = (map_zoom < 0) ? 1 : map_zoom;
-            for (uint16_t line = 0; line < (r.height() / duplicate_lines); line++) {
-                uint16_t seek_line = zoom_seek_y + ((map_zoom >= 0) ? line : line * (-map_zoom));
-                map_file.seek(4 + ((zoom_seek_x + (map_width * seek_line)) << 1));
-                map_read_line(map_line_buffer.data(), r.width());
+            if (!use_osm) {
+                prev_x_pos = x_pos;  // Note x_pos/y_pos pixel position in map file now correspond to screen rect CENTER pixel
+                prev_y_pos = y_pos;
+                // Adjust starting corner position of map per zoom setting;
+                // When zooming in the map should technically by shifted left & up by another map_zoom/2 pixels but
+                // the map_read_line_bin() function doesn't handle that yet so we're adjusting markers instead (see zoom_pixel_offset).
+                if (map_zoom > 1) {
+                    zoom_seek_x = x_pos - (float)r.width() / (2 * map_zoom);
+                    zoom_seek_y = y_pos - (float)r.height() / (2 * map_zoom);
+                } else {
+                    zoom_seek_x = x_pos - (r.width() * abs(map_zoom)) / 2;
+                    zoom_seek_y = y_pos - (r.height() * abs(map_zoom)) / 2;
+                }
+                // Read from map file and display to zoomed scale
+                int duplicate_lines = (map_zoom < 0) ? 1 : map_zoom;
+                for (uint16_t line = 0; line < (r.height() / duplicate_lines); line++) {
+                    uint16_t seek_line = zoom_seek_y + ((map_zoom >= 0) ? line : line * (-map_zoom));
+                    map_file.seek(4 + ((zoom_seek_x + (map_width * seek_line)) << 1));
+                    map_read_line_bin(map_line_buffer.data(), r.width());
+                    for (uint16_t j = 0; j < duplicate_lines; j++) {
+                        display.draw_pixels({0, r.top() + (line * duplicate_lines) + j, r.width(), 1}, map_line_buffer);
+                    }
+                }
 
-                for (uint16_t j = 0; j < duplicate_lines; j++) {
-                    display.draw_pixels({0, r.top() + (line * duplicate_lines) + j, r.width(), 1}, map_line_buffer);
+            } else {
+                // display osm tiles
+                //  Convert center GPS to a global pixel coordinate
+                double global_center_px = lon_to_pixel_x_tile(lon_, map_osm_zoom);
+                double global_center_py = lat_to_pixel_y_tile(lat_, map_osm_zoom);
+
+                // Find the top-left corner of the screen (viewport) in global pixel coordinates
+                viewport_top_left_px = global_center_px - (r.width() / 2.0);
+                viewport_top_left_py = global_center_py - (r.height() / 2.0);
+
+                // Find the tile ID that contains the top-left corner of the viewport
+                int start_tile_x = floor(viewport_top_left_px / TILE_SIZE);
+                int start_tile_y = floor(viewport_top_left_py / TILE_SIZE);
+
+                // Calculate the crucial render offset.
+                // This determines how much the first tile is shifted to align the map correctly.
+                // This value will almost always be negative or zero.
+                double render_offset_x = -(viewport_top_left_px - (start_tile_x * TILE_SIZE));
+                double render_offset_y = -(viewport_top_left_py - (start_tile_y * TILE_SIZE));
+
+                // Determine how many tiles we need to draw to fill the screen
+                int tiles_needed_x = (r.width() / TILE_SIZE) + 2;
+                int tiles_needed_y = (r.height() / TILE_SIZE) + 2;
+
+                for (int y = 0; y < tiles_needed_y; ++y) {
+                    for (int x = 0; x < tiles_needed_x; ++x) {
+                        int current_tile_x = start_tile_x + x;
+                        int current_tile_y = start_tile_y + y;
+
+                        // Calculate the final on-screen drawing position for this tile.
+                        // For the first tile (x=0, y=0), this will be the negative offset.
+                        int draw_pos_x = round(render_offset_x + x * TILE_SIZE);
+                        int draw_pos_y = round(render_offset_y + y * TILE_SIZE);
+                        if (!draw_osm_file(map_osm_zoom, current_tile_x, current_tile_y, draw_pos_x, draw_pos_y)) {
+                            // already blanked it.
+                        }
+                    }
                 }
             }
+
         } else {
             // No map data or excessive zoom; just draw a grid
-            draw_map_grid();
+            draw_map_grid(r);
         }
-
         // Draw crosshairs in center in manual panning mode
         if (manual_panning_) {
             display.fill_rectangle({r.center() - Point(16, 1) + Point(zoom_pixel_offset, zoom_pixel_offset), {32, 2}}, Color::red());
@@ -394,8 +568,9 @@ void GeoMap::paint(Painter& painter) {
 
         // Draw the other markers
         draw_markers(painter);
-        draw_scale(painter);
+        if (!use_osm) draw_scale(painter);
         draw_mypos(painter);
+        if (has_osm) draw_switcher(painter);
         set_clean();
     }
 
@@ -405,6 +580,12 @@ void GeoMap::paint(Painter& painter) {
     }
 }
 
+void GeoMap::draw_switcher(Painter& painter) {
+    painter.fill_rectangle({screen_rect().left(), screen_rect().top(), 3 * 20, 20}, Theme::getInstance()->bg_darker->background);
+    std::string_view txt = (use_osm) ? "B I N" : "O S M";
+    painter.draw_string({screen_rect().left() + 5, screen_rect().top() + 2}, *Theme::getInstance()->fg_light, txt);
+}
+
 bool GeoMap::on_keyboard(KeyboardEvent key) {
     if (key == '+' || key == ' ') return on_encoder(1);
     if (key == '-') return on_encoder(-1);
@@ -413,11 +594,26 @@ bool GeoMap::on_keyboard(KeyboardEvent key) {
 }
 
 bool GeoMap::on_touch(const TouchEvent event) {
+    if (has_osm && event.type == TouchEvent::Type::Start && event.point.x() < screen_rect().left() + 3 * 20 && event.point.y() < screen_rect().top() + 20) {
+        use_osm = !use_osm;
+        move(lon_, lat_);  // to re calculate the center for each map type
+        if (use_osm) set_osm_max_zoom();
+        redraw_map = true;
+        set_dirty();
+        return false;  // false, because with true this hits 2 times
+    }
+
     if ((event.type == TouchEvent::Type::Start) && (mode_ == PROMPT)) {
+        Point p;
         set_highlighted(true);
         if (on_move) {
-            Point p = event.point - screen_rect().center();
-            on_move(p.x() / 2.0 * lon_ratio, p.y() / 2.0 * lat_ratio);
+            if (!use_osm) {
+                p = event.point - screen_rect().center();
+                on_move(p.x() / 2.0 * lon_ratio, p.y() / 2.0 * lat_ratio, false);
+            } else {
+                p = event.point - screen_rect().location();
+                on_move(tile_pixel_x_to_lon(p.x() + viewport_top_left_px, map_osm_zoom), tile_pixel_y_to_lat(p.y() + viewport_top_left_py, map_osm_zoom), true);
+            }
             return true;
         }
     }
@@ -426,25 +622,30 @@ bool GeoMap::on_touch(const TouchEvent event) {
 
 void GeoMap::move(const float lon, const float lat) {
     const auto r = screen_rect();
-
+    bool is_changed = (lon_ != lon || lat_ != lat);
     lon_ = lon;
     lat_ = lat;
+    if (!use_osm) {
+        // Calculate x_pos/y_pos in map file corresponding to CENTER pixel of screen rect
+        // (Note there is a 1:1 correspondence between map file pixels and screen pixels when map_zoom=1)
+        GeoPoint mapPoint = lat_lon_to_map_pixel(lat_, lon_);
+        x_pos = mapPoint.x;
+        y_pos = mapPoint.y;
+        // Cap position
+        if (x_pos > (map_width - r.width() / 2))
+            x_pos = map_width - r.width() / 2;
+        if (y_pos > (map_height + r.height() / 2))
+            y_pos = map_height - r.height() / 2;
 
-    // Calculate x_pos/y_pos in map file corresponding to CENTER pixel of screen rect
-    // (Note there is a 1:1 correspondence between map file pixels and screen pixels when map_zoom=1)
-    GeoPoint mapPoint = lat_lon_to_map_pixel(lat_, lon_);
-    x_pos = mapPoint.x;
-    y_pos = mapPoint.y;
-
-    // Cap position
-    if (x_pos > (map_width - r.width() / 2))
-        x_pos = map_width - r.width() / 2;
-    if (y_pos > (map_height + r.height() / 2))
-        y_pos = map_height - r.height() / 2;
-
-    // Scale calculation
-    float km_per_deg_lon = cos(lat * pi / 180) * 111.321;  // 111.321 km/deg longitude at equator, and 0 km at poles
-    pixels_per_km = (r.width() / 2) / km_per_deg_lon;
+        // Scale calculation
+        float km_per_deg_lon = cos(lat * pi / 180) * 111.321;  // 111.321 km/deg longitude at equator, and 0 km at poles
+        pixels_per_km = (r.width() / 2) / km_per_deg_lon;
+    } else {
+        if (is_changed) {
+            set_osm_max_zoom();
+            redraw_map = true;
+        }
+    }
 }
 
 bool GeoMap::init() {
@@ -469,8 +670,7 @@ bool GeoMap::init() {
     map_bottom = sin(-85.05 * pi / 180);  // Map bitmap only goes from about -85 to 85 lat
     map_world_lon = map_width / (2 * pi);
     map_offset = (map_world_lon / 2 * log((1 + map_bottom) / (1 - map_bottom)));
-
-    return map_opened;
+    return map_opened || has_osm;
 }
 
 void GeoMap::set_mode(GeoMapMode mode) {
@@ -595,24 +795,29 @@ MapMarkerStored GeoMap::store_marker(GeoMarker& marker) {
 }
 
 void GeoMap::update_my_position(float lat, float lon, int32_t altitude) {
+    bool is_changed = (my_pos.lat != lat) || (my_pos.lon != lon);
     my_pos.lat = lat;
     my_pos.lon = lon;
     my_altitude = altitude;
-    redraw_map = true;
+    redraw_map = is_changed;
     set_dirty();
 }
 
 void GeoMap::update_my_orientation(uint16_t angle, bool refresh) {
+    bool is_changed = (my_pos.angle != angle);
     my_pos.angle = angle;
-    if (refresh) {
+    if (refresh && is_changed) {
         redraw_map = true;
         set_dirty();
     }
 }
 
+MapType GeoMap::get_map_type() {
+    return use_osm ? MAP_TYPE_OSM : MAP_TYPE_BIN;
+}
+
 void GeoMapView::focus() {
     geopos.focus();
-
     if (!geomap.map_file_opened())
         nav_.display_modal("No map", "No world_map.bin file in\n/" + adsb_dir.string() + "/ directory", ABORT);
 }
@@ -629,7 +834,7 @@ void GeoMapView::update_position(float lat, float lon, uint16_t angle, int32_t a
         geomap.set_dirty();
         return;
     }
-
+    bool is_changed = lat_ != lat || lon_ != lon || altitude_ != altitude || speed_ != speed || angle_ != angle;
     lat_ = lat;
     lon_ = lon;
     altitude_ = altitude;
@@ -644,7 +849,7 @@ void GeoMapView::update_position(float lat, float lon, uint16_t angle, int32_t a
     geopos.set_report_change(true);
 
     geomap.set_angle(angle);
-    geomap.move(lon_, lat_);
+    if (is_changed) geomap.move(lon_, lat_);
     geomap.set_dirty();
 }
 
@@ -660,19 +865,25 @@ void GeoMapView::setup() {
     geopos.set_lon(lon_);
 
     geopos.on_change = [this](int32_t altitude, float lat, float lon, int32_t speed) {
+        bool is_changed = (altitude_ != altitude) || (lat_ != lat) || (lon_ != lon) || (speed_ != speed);
         altitude_ = altitude;
         lat_ = lat;
         lon_ = lon;
         speed_ = speed;
         geopos.hide_altandspeed();
         geomap.set_manual_panning(true);
-        geomap.move(lon_, lat_);
+        if (is_changed) geomap.move(lon_, lat_);
         geomap.set_dirty();
     };
 
-    geomap.on_move = [this](float move_x, float move_y) {
-        lon_ += move_x;
-        lat_ += move_y;
+    geomap.on_move = [this](float move_x, float move_y, bool absolute) {
+        if (absolute) {
+            lon_ = move_x;
+            lat_ = move_y;
+        } else {
+            lon_ += move_x;
+            lat_ += move_y;
+        }
 
         // Stupid hack to avoid an event loop
         geopos.set_report_change(false);
@@ -769,4 +980,8 @@ MapMarkerStored GeoMapView::store_marker(GeoMarker& marker) {
     return geomap.store_marker(marker);
 }
 
+MapType GeoMapView::get_map_type() {
+    return geomap.get_map_type();
+}
+
 } /* namespace ui */
diff --git a/firmware/application/ui/ui_geomap.hpp b/firmware/application/ui/ui_geomap.hpp
index 621816192..fd8347fd7 100644
--- a/firmware/application/ui/ui_geomap.hpp
+++ b/firmware/application/ui/ui_geomap.hpp
@@ -27,6 +27,8 @@
 #include "ui.hpp"
 #include "file.hpp"
 #include "ui_navigation.hpp"
+#include "bmpfile.hpp"
+#include "mathdef.hpp"
 
 #include "portapack.hpp"
 
@@ -43,6 +45,8 @@ namespace ui {
 #define GEOMAP_RECT_WIDTH 240
 #define GEOMAP_RECT_HEIGHT (320 - 16 - GEOMAP_BANNER_HEIGHT)
 
+#define TILE_SIZE 256
+
 enum GeoMapMode {
     DISPLAY,
     PROMPT
@@ -193,9 +197,14 @@ enum MapMarkerStored {
     MARKER_LIST_FULL
 };
 
+enum MapType {
+    MAP_TYPE_OSM,
+    MAP_TYPE_BIN
+};
+
 class GeoMap : public Widget {
    public:
-    std::function<void(float, float)> on_move{};
+    std::function<void(float, float, bool)> on_move{};
 
     GeoMap(Rect parent_rect);
 
@@ -216,6 +225,7 @@ class GeoMap : public Widget {
     void set_tag(std::string new_tag) {
         tag_ = new_tag;
     }
+    MapType get_map_type();
 
     void set_angle(uint16_t new_angle) {
         angle_ = new_angle;
@@ -246,8 +256,22 @@ class GeoMap : public Widget {
     void draw_markers(Painter& painter);
     void draw_mypos(Painter& painter);
     void draw_bearing(const Point origin, const uint16_t angle, uint32_t size, const Color color);
-    void draw_map_grid();
-    void map_read_line(ui::Color* buffer, uint16_t pixels);
+    void draw_map_grid(ui::Rect r);
+    void draw_switcher(Painter& painter);
+    void map_read_line_bin(ui::Color* buffer, uint16_t pixels);
+    // open street map related
+    uint8_t find_osm_file_tile();
+    void set_osm_max_zoom();
+    bool draw_osm_file(int zoom, int tile_x, int tile_y, int relative_x, int relative_y);
+    int lon2tile(double lon, int zoom);
+    int lat2tile(double lat, int zoom);
+    double lon_to_pixel_x_tile(double lon, int zoom);
+    double lat_to_pixel_y_tile(double lat, int zoom);
+    double tile_pixel_x_to_lon(int x, int zoom);
+    double tile_pixel_y_to_lat(int y, int zoom);
+    uint8_t map_osm_zoom{3};
+    double viewport_top_left_px = 0;
+    double viewport_top_left_py = 0;
 
     bool manual_panning_{false};
     bool hide_center_marker_{false};
@@ -258,11 +282,11 @@ class GeoMap : public Widget {
     uint16_t map_width{}, map_height{};
     int32_t map_center_x{}, map_center_y{};
     int16_t map_zoom{1};
+
     float lon_ratio{}, lat_ratio{};
     double map_bottom{};
     double map_world_lon{};
     double map_offset{};
-
     float x_pos{}, y_pos{};
     float prev_x_pos{32767.0f}, prev_y_pos{32767.0f};
     float lat_{};
@@ -278,7 +302,9 @@ class GeoMap : public Widget {
 
     int markerListLen{0};
     GeoMarker markerList[NumMarkerListElements];
-    bool redraw_map{false};
+    bool redraw_map{true};
+    bool use_osm{false};
+    bool has_osm{false};
 };
 
 class GeoMapView : public View {
@@ -313,6 +339,8 @@ class GeoMapView : public View {
     void update_my_position(float lat, float lon, int32_t altitude);
     void update_my_orientation(uint16_t angle, bool refresh = false);
 
+    MapType get_map_type();
+
     std::string title() const override { return "Map view"; };
 
     void clear_markers();
diff --git a/firmware/baseband/proc_epirb.cpp b/firmware/baseband/proc_epirb.cpp
index 358864e22..ad169a2f8 100644
--- a/firmware/baseband/proc_epirb.cpp
+++ b/firmware/baseband/proc_epirb.cpp
@@ -85,7 +85,8 @@ void EPIRBProcessor::payload_handler(const baseband::Packet& packet) {
     }
 }
 
-void EPIRBProcessor::on_message(const Message*) {
+void EPIRBProcessor::on_message(const Message* const message) {
+    (void)message;  // Unused in this processor
 }
 
 int main() {
diff --git a/firmware/baseband/proc_fsk_rx.cpp b/firmware/baseband/proc_fsk_rx.cpp
index 930df3bf7..4aec1a32e 100644
--- a/firmware/baseband/proc_fsk_rx.cpp
+++ b/firmware/baseband/proc_fsk_rx.cpp
@@ -33,9 +33,7 @@
 #include <cstdint>
 #include <cstddef>
 
-#ifndef M_PI
-#define M_PI 3.14159265358979323846
-#endif
+#include "mathdef.hpp"
 
 float FSKRxProcessor::detect_peak_power(const buffer_c8_t& buffer, int N) {
     int32_t power = 0;
diff --git a/firmware/baseband/proc_jammer.cpp b/firmware/baseband/proc_jammer.cpp
index cce46029a..19c832e99 100644
--- a/firmware/baseband/proc_jammer.cpp
+++ b/firmware/baseband/proc_jammer.cpp
@@ -30,9 +30,7 @@
 #include <random>
 #include <cmath>
 
-#ifndef M_PI
-#define M_PI 3.14159265358979323846f
-#endif
+#include "mathdef.hpp"
 
 void JammerProcessor::execute(const buffer_c8_t& buffer) {
     if (!configured) return;
diff --git a/firmware/common/adsb.hpp b/firmware/common/adsb.hpp
index ab4172925..68d9264b3 100644
--- a/firmware/common/adsb.hpp
+++ b/firmware/common/adsb.hpp
@@ -91,7 +91,7 @@ const float adsb_lat_lut[58] = {
     83.07199445, 83.99173563, 84.89166191, 85.75541621,
     86.53536998, 87.00000000};
 
-const float PI = 3.14159265358979323846;
+#include "mathdef.hpp"
 
 const float NZ = 15.0;
 
diff --git a/firmware/common/bmpfile.cpp b/firmware/common/bmpfile.cpp
index d39c2fb6e..689984740 100644
--- a/firmware/common/bmpfile.cpp
+++ b/firmware/common/bmpfile.cpp
@@ -52,10 +52,10 @@ void BMPFile::close() {
     bmpimage.close();
 }
 
-// creates a new bmp file. for now, hardcoded to 3 byte colour depth
+// creates a new bmp file. hardcoded to 3 byte (24-bit) colour depth
 bool BMPFile::create(const std::filesystem::path& file, uint32_t x, uint32_t y) {
     is_opened = false;
-    is_read_ony = true;
+    is_read_only = true;
     bmpimage.close();  // if already open, close before open a new
     if (file_exists(file)) {
         delete_file(file);  // overwrite
@@ -85,7 +85,7 @@ bool BMPFile::create(const std::filesystem::path& file, uint32_t x, uint32_t y)
     bmpimage.write(&bmp_header, sizeof(bmp_header_t));
     file_pos = bmp_header.image_data;
     is_opened = true;
-    is_read_ony = false;
+    is_read_only = false;
     if (!expand_y(y)) return false;  // will fill with 0, and update header data
     seek(0, 0);
     return true;
@@ -94,30 +94,36 @@ bool BMPFile::create(const std::filesystem::path& file, uint32_t x, uint32_t y)
 // opens the file and parses header data. return true on success
 bool BMPFile::open(const std::filesystem::path& file, bool readonly) {
     is_opened = false;
-    is_read_ony = true;
-    bmpimage.close();  // if already open, close before open a new
+    is_read_only = true;
+    bmpimage.close();
 
     auto result = bmpimage.open(file, readonly, false);
     if (!result.value().ok()) return false;
     file_pos = 0;
     bmpimage.seek(file_pos);
-    auto read_size = bmpimage.read(&bmp_header, sizeof(bmp_header_t));
-    if (!((bmp_header.signature == 0x4D42) &&                               // "BM" Signature
-          (bmp_header.planes == 1) &&                                       // Seems always to be 1
-          (bmp_header.compression == 0 || bmp_header.compression == 3))) {  // No compression
+    bmpimage.read(&bmp_header, sizeof(bmp_header_t));
+    if (!((bmp_header.signature == 0x4D42) &&
+          (bmp_header.planes == 1) &&
+          (bmp_header.compression == 0 || bmp_header.compression == 3))) {
         return false;
     }
-    char buffer[257];
+
     switch (bmp_header.bpp) {
+        case 8:
+            type = 4;
+            byte_per_px = 1;
+            // bmpimage.seek(sizeof(bmp_header_t));
+            // bmpimage.read(color_palette, 1024);
+            return false;  // niy
+            break;
+
         case 16:
-            file_pos = 0x36;
-            memset(buffer, 0, 16);
-            bmpimage.read(buffer, 16);
             byte_per_px = 2;
-            if (buffer[1] == 0x7C)
-                type = 3;  // A1R5G5B5
-            else
-                type = 0;  // R5G6B5
+            type = 5;
+            if (bmp_header.compression == 3) {
+                return false;
+            }  // niy
+
             break;
         case 24:
             type = 1;
@@ -130,12 +136,11 @@ bool BMPFile::open(const std::filesystem::path& file, bool readonly) {
         default:
             // not supported
             return false;
-            break;
     }
-    byte_per_row = (bmp_header.width * byte_per_px % 4 == 0) ? bmp_header.width * byte_per_px : (bmp_header.width * byte_per_px + (4 - ((bmp_header.width * byte_per_px) % 4)));
+    byte_per_row = (bmp_header.width * byte_per_px + 3) & ~3;
     file_pos = bmp_header.image_data;
     is_opened = true;
-    is_read_ony = readonly;
+    is_read_only = readonly;
     currx = 0;
     curry = 0;
     return true;
@@ -161,20 +166,24 @@ bool BMPFile::read_next_px(ui::Color& px, bool seek = true) {
     auto res = bmpimage.read(buffer, byte_per_px);
     if (res.is_error()) return false;
     switch (type) {
-        case 0:  // R5G6B5
-        case 3:  // A1R5G5B5
-            if (!type)
-                px = ui::Color((uint16_t)buffer[0] | ((uint16_t)buffer[1] << 8));
-            else
-                px = ui::Color(((uint16_t)buffer[0] & 0x1F) | ((uint16_t)buffer[0] & 0xE0) << 1 | ((uint16_t)buffer[1] & 0x7F) << 9);
+        case 5: {
+            uint16_t color16 = (uint16_t)buffer[0] | ((uint16_t)buffer[1] << 8);
+            px = ui::Color(color16);  // has glitches!
             break;
+        }
+        case 2:  // 32
+            px = ui::Color(buffer[2], buffer[1], buffer[0]);
+            break;
+
+        case 4: {  // 8-bit
+            // uint8_t index = buffer[0];
+            //  px = ui::Color(color_palette[index][2], color_palette[index][1], color_palette[index][0]);  // Palette is BGR
+            // px = ui::Color(buffer[0]);  // niy, since needs a lot of ram for the palette
+            break;
+        }
         case 1:  // 24
         default:
             px = ui::Color(buffer[2], buffer[1], buffer[0]);
-
-            break;
-        case 2:  // 32
-            px = ui::Color(buffer[2], buffer[1], buffer[0]);
             break;
     }
     if (seek) advance_curr_px();
@@ -188,23 +197,23 @@ void BMPFile::set_bg_color(ui::Color background) {
 }
 
 // delete bg color. default. creation or expansion will be fast, but the file will contain random garbage. no problem if you write all pixels later.
-void BMPFile::delete_db_color() {
+void BMPFile::delete_bg_color() {
     use_bg = false;
 }
 
 // writes a color data to the current position, and advances 1 px. true on success, false on error
 bool BMPFile::write_next_px(ui::Color& px) {
-    if (!is_opened) return false;
-    if (is_read_ony) return false;
+    if (!is_opened || is_read_only) return false;
     uint8_t buffer[4];
     switch (type) {
+        case 5:
         case 0:  // R5G6B5
         case 3:  // A1R5G5B5
             if (!type) {
-                buffer[0] = (px.r() << 3) | (px.g() >> 3);  // todo test in future
+                buffer[0] = (px.r() << 3) | (px.g() >> 3);
                 buffer[1] = (px.g() << 5) | px.b();
             } else {
-                buffer[0] = (1 << 7) | (px.r() << 2) | (px.g() >> 3);  // todo test in future
+                buffer[0] = (1 << 7) | (px.r() << 2) | (px.g() >> 3);
                 buffer[1] = (px.g() << 5) | px.b();
             }
             break;
@@ -220,6 +229,8 @@ bool BMPFile::write_next_px(ui::Color& px) {
             buffer[0] = px.b();
             buffer[3] = 255;
             break;
+        case 4:  // 8-bit
+            return false;
     }
     auto res = bmpimage.write(buffer, byte_per_px);
     if (res.is_error()) return false;
@@ -260,7 +271,7 @@ bool BMPFile::expand_y(uint32_t new_y) {
     if (!is_opened) return false;  // not yet opened
     uint32_t old_height = get_real_height();
     if (new_y < old_height) return true;  // already bigger
-    if (is_read_ony) return false;        // can't expand
+    if (is_read_only) return false;       // can't expand
     uint32_t delta = (new_y - old_height) * byte_per_row;
     bmp_header.size += delta;
     bmp_header.data_size += delta;
diff --git a/firmware/common/bmpfile.hpp b/firmware/common/bmpfile.hpp
index efaf13818..f3709bd23 100644
--- a/firmware/common/bmpfile.hpp
+++ b/firmware/common/bmpfile.hpp
@@ -47,12 +47,12 @@ class BMPFile {
     uint32_t get_width();
     bool is_bottomup();
     void set_bg_color(ui::Color background);
-    void delete_db_color();
+    void delete_bg_color();
 
    private:
     bool advance_curr_px(uint32_t num);
     bool is_opened = false;
-    bool is_read_ony = true;
+    bool is_read_only = true;
 
     File bmpimage{};
     size_t file_pos = 0;
@@ -64,6 +64,7 @@ class BMPFile {
     uint32_t currx = 0;
     uint32_t curry = 0;
     ui::Color bg{};
+    // uint8_t color_palette[256][4];
     bool use_bg = false;
 };
 
diff --git a/firmware/common/complex.hpp b/firmware/common/complex.hpp
index ac24b0ab5..b8f184e3a 100644
--- a/firmware/common/complex.hpp
+++ b/firmware/common/complex.hpp
@@ -26,7 +26,9 @@
 #include <complex>
 #include <cmath>
 
-constexpr float pi{3.141592653589793238462643383279502884f};
+#include "mathdef.hpp"
+
+constexpr float pi{M_PI};
 
 namespace std {
 
diff --git a/firmware/common/mathdef.hpp b/firmware/common/mathdef.hpp
new file mode 100644
index 000000000..52283bcac
--- /dev/null
+++ b/firmware/common/mathdef.hpp
@@ -0,0 +1,4 @@
+#pragma once
+
+#define PI 3.1415926535897932384626433832795
+#define M_PI PI
\ No newline at end of file
diff --git a/firmware/common/sonde_packet.cpp b/firmware/common/sonde_packet.cpp
index 9bda83d15..0878f51f9 100644
--- a/firmware/common/sonde_packet.cpp
+++ b/firmware/common/sonde_packet.cpp
@@ -47,7 +47,7 @@ static uint8_t calfrchk[51];        // so subframes are preserved while populate
 #define pos_GPSecefY 0x114  // 0x118  // 4 byte (not actually used since Y and Z are following X, and grabbed in that same loop)
 #define pos_GPSecefZ 0x118  // 0x11C  // 4 byte (same as Y)
 
-#define PI 3.1415926535897932384626433832795  // 3.1416 //(3.1415926535897932384626433832795)
+#include "mathdef.hpp"
 
 Packet::Packet(
     const baseband::Packet& packet,
diff --git a/sdcard/OSM/readme.md b/sdcard/OSM/readme.md
new file mode 100644
index 000000000..050e6d2eb
--- /dev/null
+++ b/sdcard/OSM/readme.md
@@ -0,0 +1,14 @@
+Download OSM Tile files to the root of the SD card to the folder: /OSM/
+There must be the standard directory structure of OSM ( /OSM/{zoom}/{x}/{y}.bmp).
+The tile files must be BMP 24 bit color depth format.
+
+
+To disable this function, simply delete the subfolders from this OSM folder.
+
+
+There is a website, that can download tile files in the given format and structure: https://pposm.creativo.hu
+You select the area you want to download, and the maximum zoom level. There will be a size estimation.
+Then Click on start download button, and browse the sd cards /OSM folder. Then click select and enable (twice).
+The download will begin. Depending on the area size and the max zoom level it can take a lot of time.
+With this app you can download multiple regions in multiple depths, just run it again. 
+For the site to work, you must use up to date Chromium based browser.