The right online tool to georeference a scanned map depends on your goal. For archiving, a tool like Map Warper aligns a static image to a modern map. However, to create a new, editable vector map from a scan, you need an integrated cartography editor. Gratic is built for this workflow, where georeferencing is the first step in drawing, not the final output.
The real goal of georeferencing your map
The best tool for you depends on whether you want to display a static, historical image online or use it as a reference for drawing a new, live map. The distinction is critical because it separates tools designed for archiving from tools designed for production cartography. One type of tool treats the scanned image as the final product, while the other treats it as a temporary guide. Understanding your own purpose is the first step in choosing the right application, as they solve fundamentally different problems, even if they share a common technical term.
Many online tools are built for what I call 'georeferencing for display'. Their primary function is to take a static image of a map—often a historical one—and warp it so it can be overlaid on a modern web map. A service like Map Warper excels at this. It is an open-source project designed to let people upload scans and collaboratively place control points to align them.
The result is a georeferenced image, often a GeoTIFF, or a tile layer you can view in a browser. This is invaluable for libraries, historical societies, and researchers who want to make archival material accessible and comparable to present-day geography. The original map artifact is the focus, and the goal is to preserve and present it accurately in a new context. The process ends when the image is correctly placed.
My focus when building Gratic was on 'georeferencing for drawing'. For a cartographer making a new orienteering map, an old map or an aerial photograph is not the final product; it is source material. The goal is not to display the old scan, but to extract its information into a new, clean, and standardized vector format. The georeferenced image is just a temporary layer, like tracing paper.
You draw over it using vector pens that create distinct objects—a path, a building, a contour line—with proper symbols. When the tracing is done, you can hide or delete the scanned image entirely. The final output is a structured file, like the OCAD files Gratic produces, that contains live data, not a warped static image. I built the georeferencing feature in Gratic to serve this specific workflow, integrating it directly into the drawing environment.
How a drawing-focused tool handles georeferencing
A drawing-focused tool treats the scanned map as just another layer within the editor, letting you trace over it with precise vector pens. The process is not a separate utility but an integrated part of the map-making workflow. Instead of exporting a georeferenced image file and then importing it into a different drawing program, you do everything in one place. This was a core design principle for Gratic: reduce the number of steps and applications needed to get from a source map to a finished sheet. The entire process, from uploading the scan to drawing the final symbol, happens in a single browser tab.
In Gratic, the workflow begins when you upload your scanned map image directly into your project. The application then prompts you to add control points. You click a known location on your scanned map—a road intersection, a building corner—and then click the corresponding point on the base map already loaded in the editor. Gratic pulls in vector data from national mapping services and generates contours from elevation data, so you are aligning your scan to a live, accurate map from the start. After you have placed a few points, the application warps the scanned image in the background to fit the underlying geography. It is now a georeferenced layer inside your map file, ready for you to work with.
Once the scanned map is aligned, it behaves like any other layer in a cartography editor. You can adjust its transparency, making it fainter so you can clearly see the new vector lines you are drawing on top. You can toggle its visibility on and off to check your progress against the base map or to see your new work without the distraction of the old lines. You are not editing the image; you are using it as a guide for creating new vector objects with our standard orienteering symbol sets.
The final product is the vector data you create. When you save, you are saving a file that opens in OCAD, containing all the new objects you drew. The temporary scanned image has served its purpose and is no longer the focus.
Trade-offs between online georeferencing tools
The main trade-off is between tools designed for simple public collaboration on historical images and specialized tools built for a precise cartographic workflow. General-purpose tools are often more accessible and may be free, but they typically do not support the specific needs of creating a new, standardized map. They solve the problem of placing an image on a map, but not the problem of creating a new map from that image. This distinction in purpose leads to very different feature sets and user experiences.
Tools like Map Warper are excellent for their intended purpose: crowdsourcing the georeferencing of archival maps. The interface is straightforward for placing control points, and its open-source, web-based nature makes it highly accessible for collaborative projects. However, it is not a drawing editor. Its job ends once the image is rectified. To create a new vector map from its output, you would still need to download the resulting file and import it into a separate desktop GIS or cartography program like OCAD. This multi-step process, switching between different applications, is exactly what I wanted to avoid when I designed Gratic.
Other online GIS platforms might include georeferencing as one feature among hundreds. These are powerful, general-purpose systems, but they often lack the specialized tools a cartographer needs for making an orienteering map. They may not have the correct ISOM symbol sets built in, or their drawing pens might not behave in the way a mapper expects for creating smooth curves or patterned lines. The workflow can be complex because the tool is designed to serve many different industries.
My goal with Gratic was to build an editor that is opinionated and focused. It does one job—creating orienteering and terrain maps—and every feature, including georeferencing, is built to serve that single purpose as efficiently as possible. It is a trade-off of breadth for depth.
Frequently asked questions
Can I use Gratic just to georeference an image and export it? No, Gratic is a vector cartography editor, not a georeferencing utility. The georeferenced image exists only as a temporary tracing layer inside the editor. The primary output from Gratic is a vector map file that opens in OCAD, containing the new features you have drawn, not a georeferenced raster file like a GeoTIFF.
Do I need to supply my own base map data for alignment? No. When you define your map area in Gratic, the editor automatically imports available vector data from national mapping services and generates contour lines from our elevation data. You align your scanned map to this live, pre-existing data, which ensures your new map is correctly placed from the start.
Will my final map file work with other software? Yes. From the beginning, I knew that mappers need to move between tools. Gratic saves files in a format that opens directly in OCAD. This ensures you are never locked into our editor and can integrate Gratic into a workflow that includes other desktop cartography software.
Is the georeferencing process difficult to learn? The process is integrated directly into the map creation workflow. If you can identify a few matching points between your scanned map and a modern map—like two road junctions or building corners—you can georeference the image. The tool is designed to get you from a scan to a drawing layer in a few minutes, without needing a background in GIS.