How to Import and Edit Maps in OziExplorerOziExplorer is a powerful Windows-based mapping and GPS navigation application used by hikers, surveyors, pilots, and fieldworkers to manage raster maps, track GPS routes, and plan navigation. This guide walks through everything you need to know to import maps into OziExplorer, calibrate and edit them, and optimize them for use with GPS devices. It assumes you have a working copy of OziExplorer installed and at least one digital map file (JPEG, TIFF, PNG, or BMP) or a scanned paper map.
What you’ll need
- A Windows PC with OziExplorer installed (standard or Trial).
- Digital map files (JPEG, PNG, TIFF, BMP) or scanned maps saved on your computer.
- Optional: GPS device (supported models) or a GPX/KML track file.
- Optional: Map calibration data (world file, .map file from other users, or control points).
1. Preparing your map files
Before importing, organize your maps in folders and ensure file names are descriptive (for example: “Topo_Oxfordshire_1_25000.jpg”). If you’re scanning paper maps:
- Scan at a resolution that preserves detail (300–600 DPI recommended).
- Save as a lossless or high-quality JPEG/PNG/TIFF to avoid artifacts.
- Remove borders or titles if you prefer — you can crop later in OziExplorer.
2. Creating a new map in OziExplorer
- Open OziExplorer.
- From the File menu choose “Open Map” (or press Ctrl+O).
- Browse to and select the image file and click Open.
- OziExplorer will ask if you want to create a new map file (.map) — click Yes.
- The program will open the Map Image window showing the imported image and the Map Calibration window where you will add control points.
At this stage, the image is imported but not yet georeferenced — it has no real-world coordinates attached. You must add control points to tie image pixels to latitude/longitude or grid coordinates.
3. Adding control points (calibration)
Calibration (often called “georeferencing”) is the process of assigning coordinates to points on the image so OziExplorer knows where the map fits on Earth.
Steps:
- In the Map Calibration window, click “New” to add control points.
- For each control point:
- Click a recognizable location on the map image (e.g., a road intersection, trig point, or map grid corner).
- Enter the real-world coordinates for that point. You can input:
- Latitude and longitude (in degrees, minutes, seconds or decimal degrees), or
- Grid coordinates (e.g., UTM Easting/Northing), or
- Map grid references used on the map (e.g., British National Grid).
- Add at least three well-spaced control points. For better accuracy, use 4–6 points placed near the corners and center of the map.
- After adding points, check the RMS (root mean square) error value shown in the calibration window. Lower RMS indicates a better fit; aim for values as small as possible (typically under 10–20 meters for good scans, but acceptable thresholds vary with map scale and source).
Tips for choosing control points:
- Use obvious, unmoving features: road intersections, building corners, trig pillars.
- Avoid features that might have changed (new roads, temporary features).
- Spread points across the image — clustering causes local accuracy but poor global fit.
4. Choosing the best projection and datum
OziExplorer supports multiple datums and projections. When entering control coordinates, ensure you select the correct datum (e.g., WGS84, NAD83, OSGB36) and projection (if using grid coordinates like UTM or national grids). If the map includes a projection note or grid ticks, match OziExplorer settings to those. Incorrect datum/projection selection produces systematic offsets.
To set datum/projection:
- In the Map Calibration window, click the Datum/Projection button.
- Choose the appropriate datum (WGS84 is common for GPS-based coordinates).
- If you’re using UTM or a national grid, select that projection and the correct zone.
5. Refining calibration and using polynomial transforms
OziExplorer uses polynomial transforms to convert pixel coordinates to map coordinates. The default linear (1st order) transform is fine for many maps, but scanned or distorted maps may need higher-order polynomials (2nd or 3rd order) to correct warping.
How to decide:
- If RMS error is high and errors vary across the map, try 2nd or 3rd order transforms.
- Be cautious: higher-order polynomials can “overfit” if you don’t have enough control points.
To change transform order:
- In the Map Calibration window, select the Polynomial order (1, 2, or 3).
- Recalculate and observe the RMS error and residuals.
6. Saving the map and exporting calibration
After satisfactory calibration:
- Click OK in the Map Calibration window.
- Save the map file — OziExplorer will create a .map file (text format) that stores control points, datum, projection, and other metadata.
- Keep the original image alongside the .map file — OziExplorer references the image path. If you move the image later, update the .map file or use the “Replace map image” feature.
You can also export calibration to formats that other programs understand:
- World files (.wld) for simple georeferencing (may lose datum/projection).
- GeoTIFF (if you raster-edit and export with georeference).
- Sharing the .map file allows other OziExplorer users to use your calibrated map.
7. Editing maps: cropping, rotating, and stitching
Cropping:
- Use an external image editor (e.g., IrfanView, GIMP, Photoshop) or OziExplorer’s “Trim Map Image” to remove margins and reduce file size.
- After cropping, open the .map file and use OziExplorer’s “Edit Map Image” → “Map Image Properties” to re-calibrate if needed.
Rotating:
- If scan is tilted, rotate in an external editor before calibration, or use OziExplorer’s rotation features and adjust control points afterward.
Stitching (creating larger maps from tiles):
- Use the “Create Map from Images” or third-party tools to stitch adjacent map tiles into one large image before calibrating.
- Alternatively, calibrate individual tiles and load them together in OziExplorer — Ozi will align maps based on shared coordinates.
8. Working with multiple maps and map sets
OziExplorer can manage many maps. Use the “Maps” menu to:
- Add maps to your map list so they’re available while navigating.
- Set map priority/zoom levels: define which map displays at certain zoom scales to avoid overlapping or incorrect display.
- Use “Map Information” to edit metadata like map name, description, and recommended zoom range.
Organize maps into folders by region or scale. Consider naming conventions like Region_Scale_Date.map for easy sorting.
9. Using maps with GPS tracks and waypoints
Once a map is calibrated:
- Load GPS tracks (GPX, OziExplorer .plt) and waypoints to view your position on the map.
- To display live GPS: connect your GPS device via USB/serial/Bluetooth, configure the correct COM port and baud rate in Options → GPS, and click the GPS connect button.
- You can also import/export waypoints and tracks to common formats (GPX is widely supported).
10. Troubleshooting common problems
- Map won’t align: check datum and projection, add more control points, or switch polynomial order.
- High RMS error: remove erroneous control points and re-add accurate ones.
- Image path broken: if you move image files, OziExplorer can’t find them — use “Replace map image” or update paths in the .map file.
- Distorted scans: try higher-order polynomials or re-scan at higher quality with minimal physical distortion.
11. Advanced tips
- Use grid intersection points (if present on the map) as reliable control points with known coordinates.
- For best GPS accuracy, calibrate maps using coordinates from a recent GPS survey rather than printed coordinate labels (if available).
- Maintain a backup of original scanned images and .map files.
- For professional workflows, consider converting mosaics to GeoTIFFs with embedded georeference for easier use in GIS software.
Example workflow (concise)
- Scan map at 300–600 DPI, save as PNG.
- Open image in OziExplorer → create new map.
- Add 4–6 control points across the image; choose correct datum (WGS84/OSGB36).
- Check RMS error; try 2nd-order polynomial if needed.
- Save .map file and add map to your map list.
- Connect GPS or load GPX tracks to use the map in the field.
Further resources
- OziExplorer’s help file (built into the program) contains detailed references for datum settings and file formats.
- Online user forums and communities often share pre-calibrated .map files for popular map series.
This guide gives a step-by-step approach to importing, calibrating, editing, and using maps in OziExplorer. Follow the calibration best practices and keep backups of your images and .map files to ensure reliable navigation and accurate mapping.
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