update documentation to reflect experimental

Author: error414

docs/Terrain.md

@@ -1,36 +1,13 @@
 # Terrain
-
-<div style="
-  background-color: #fff3e0;
-  border-left: 5px solid #f57c00;
-  border-radius: 4px;
-  padding: 12px 16px;
-  display: flex;
-  align-items: center;
-  gap: 10px;
-">
-  <span style="font-size: 20px;">⚠️</span>
-  <div>
-    <strong style="color: #e65100;">Experimental</strong>
-    <p style="margin: 2px 0 0 0; color: #bf360c; font-size: 14px;">
-      This feature is experimental. Use it with caution.
-    </p>
-  </div>
-</div>
-
-```mermaid
-flowchart TD
-    SD[Terrain data on SD card]
-    GPS[GPS position]
-    BARO[Baro altitude]
-    AGL[Computed AGL]
-
-    SD --> AGL
-    GPS --> AGL
-    BARO --> AGL
+```
+┌─────────────────────────────────────────────────┐
+│  ===Experimental===                             │
+│  This feature is experimental. Use it with      │
+│  caution.                                       │
+└─────────────────────────────────────────────────┘
 ```
 
-This feature is available **only on H7-based flight controllers with an SD card** (preferably SDIO). Due to the high CPU load
+This feature is available **only on H7-based and F4-based flight controllers with an SD card** (preferably SDIO). Due to the high CPU load
 and SD card read speed requirements of terrain data processing, it is not supported on weaker hardware.
 
 This feature in iNav determines the model’s altitude above ground level using preloaded elevation maps
@@ -82,4 +59,15 @@ them to display altitude above terrain.
 Finally, it is **strongly recommended to use only high-quality, branded SD cards** from reputable manufacturers. The terrain
 system is sensitive to SD card read speed and reliability, and low-quality or counterfeit cards may cause read errors,
 display dropouts, or automatic disabling of the feature during flight. Using a quality SD card significantly improves the
-stability and reliability of the terrain feature.
+stability and reliability of the terrain feature.
+
+# TL;DR
+
+- **H7/F4 flight controller** with SD card required
+- Format SD card using [SD Memory Card Formatter](https://www.sdcard.org/downloads/formatter/sd-memory-card-formatter-for-windows-download/) (max 4 GB partition)
+- Generate terrain data at https://terrain.ardupilot.org/ — select **SRTM1 (30 m)**
+- Delete `FREESPAC.E` from SD card root before copying files (use external card reader, not MSC)
+- Enable via CLI: `set terrain_enabled = ON` + `save`
+- Enable **Rangefinder distance** OSD element to see altitude above terrain
+- ⚠️ Displayed value is **informational only** — not used for navigation or altitude control
+- Use only **high-quality branded SD cards**