A GeoTIFF Map Editor That Runs Online and Keeps Your Imagery Private

You have a georeferenced raster. The orthophoto from yesterday’s flight, a scanned survey sheet from a national archive, a satellite chip that came down with the tasking. Today the ways to work with it are bad in three different directions: desktop GIS opens it after an install and a learning curve, a cloud platform opens it after you hand your imagery to somebody else’s servers, and a free web viewer opens it and then does nothing at all. Look at the pixels, close the tab.

MapGridder now opens a GeoTIFF directly on the map. The file is read on your device, it places itself from the georeferencing baked into it, and everything the app already does is waiting on top: MGRS and metric grids, tactical symbols, measurements, routes, and a paper-sized export. Your imagery becomes a gridded map, and the pixels never leave your machine.

What happens when you import one

Add the file the way you add any reference image. It is decoded on your device, the georeferencing inside it is converted into four corners on the real world, and the imagery appears there. The map moves to meet it. Nothing is dragged, scaled, or eyeballed into position.

Two details are worth knowing, because they are where most tools give up. If the survey was not flown square to north, the rotation recorded in the file is honored rather than flattened into an upright rectangle. And the empty collar around a flight area, the part that is not really data, comes in transparent, so the orthophoto sits on the basemap instead of inside a black frame.

From that moment it is an ordinary overlay: fade it to see the basemap through it, hide it, reorder it, and draw whatever you like above it. Here is the slice of the format that opens:

• Coordinate systems: lat/long (WGS 84), Web Mercator, and every UTM zone. That last one matters most: drone mapping software writes the local UTM zone by default, and US federal orthoimagery arrives the same way.
• Imagery: color and greyscale, palette-color map scans, and 16-bit satellite products stretched to something you can actually see.
• Big files: tiled rasters open from their embedded overview levels, so a very large sheet appears in seconds instead of decoding at full resolution. The ceiling is 25 MB per file.
• Everything else: refused by name. A file in an unsupported coordinate system tells you which system it uses and what to re-export it as, which beats imagery quietly landing two hundred meters off. A plain TIFF with no georeferencing at all is not an error either: it lands at the map center for hand anchoring, exactly like a photo.

Operators: yesterday’s flight, today’s briefing sheet

Basemap imagery is months or years old. The orthophoto you flew yesterday shows the vehicle tracks, the new berm, the vegetation as it stands this week. Bring it in, turn on MGRS, and that imagery becomes addressable: every feature on it carries a grid reference that a radio, a paper map, and a handheld GPS all agree on. Put unit symbols and control measures where they belong, measure the approach, and hand out a sheet at a real scale instead of a screenshot.

It is the same planning loop you already run, over your own imagery instead of somebody else’s tiles. Export it as a paper map at true scale when the plan is ready.

Milsim organizers: the actual site, not a sketch of it

Site maps for an airsoft or milsim event are usually a hand drawing or a screenshot with squares painted over it, and both fall apart the moment two squads describe the same treeline differently. A morning of flying gives you the real site, and under a real grid it turns into the reference everyone briefs from: objectives numbered, boundaries drawn, respawns marked, one sheet per element.

Because the grid is a genuine coordinate system rather than painted lines, a square called over the radio matches what a GPS shows in the field. See how the rest of the kit fits together on the milsim map planning page.

Analysts: open the raster where the work already happens

Looking at a raster usually costs you something first: install desktop GIS and learn it, or push the file into a platform and wait on the approval chain that any upload of source imagery triggers. Opening it in a browser tab removes both. The file is read locally, so there is no transfer to justify and nothing to request.

Once it is on the map it is not a picture in a viewer. Measure across it, trace features, read any point in the grid your report is written in, and take the vector work back out in a format other tools read: export what you drew as GeoJSON.

Private by design

The decoding happens in your browser. The pixels are read from the file on your device, drawn onto your map, and kept in your browser so the overlay is still there next time you open it. They are not sent to us. When you save a map, the position the imagery occupies travels with it; the imagery itself stays where it started.

For most people that is a pleasant property. For some it is the entire decision. Imagery that cannot be uploaded is imagery that cannot be worked on in a web tool, which is exactly why so much of this work is still done on a laptop under a desk. Reading the file locally removes the conflict instead of asking anyone to make an exception.

Organizations that need this inside their own network, air-gapped or behind their own controls, and with a commercial license to match, can run MapGridder on their own infrastructure. The same holds for imagery heavier than the browser limit, or imagery that lives in your own storage.

Import a GeoTIFF, step by step

1. Open the map and choose File → Overlay / GRG, then Upload file.
2. Pick your .tif or .tiff. It decodes on your device and lands on its own coordinates.
3. Lower the opacity if you want the basemap showing through, and raise it again once you have checked the fit.
4. Turn on the grid you brief from: MGRS, UTM, lat/long, or a custom metric grid with row and column labels.
5. Work on top of the imagery: symbols, drawings, waypoints, measurements, routes.
6. Capture the screen, or use Export as Map for a titled image or a paper-sized PDF at a true scale. Export needs a free account.

Frequently asked questions

Have a raster sitting in a folder because opening it was too much trouble? Put it on the map, give it a grid, and see what it looks like as a working sheet.