Digital elevation model data reaches orienteering map editors through raster grid files, point clouds, or indexed elevation tiles. Desktop tools like OCAD and OpenOrienteering Mapper require local file ingestion, manual coordinate referencing, and external contour generation routines. In Gratic, we pull elevation data directly into a browser tab tile by tile, turning selected bounding boxes into vector contours alongside vector data from national mapping services with nothing to install.
How desktop editors process DEM files for contour generation
Desktop editors generate contours by calculating isolines across imported raster height grids or dense point-cloud files stored on local disks. The software interpolates elevation values between adjacent grid points, traces continuous paths of equal height according to chosen contour intervals, and stores those lines as editable vector curves within the local project file.
In standard desktop workflows using OCAD or OpenOrienteering Mapper, the cartographer downloads digital elevation models from an external survey archive. These files typically arrive as GeoTIFF rasters, ASCII XYZ grids, or raw LAS and LAZ point-cloud datasets. The cartographer imports the file into the local application, verifies the coordinate system, and sets vertical intervals such as 2.5 or 5 metres. The desktop engine parses the entire grid into memory, runs a surface interpolation routine, and outputs raw contour geometry. Because raw contours derived directly from digital elevation models contain micro-relief noise, mappers frequently spend hours smoothing lines to conform to International Specification for Orienteering Maps standards.
When using standalone open-source software like OpenOrienteering Mapper, mappers often supplement the tool with desktop GIS suites to process elevation data before drawing begins. Tools like QGIS or GDAL convert raw LiDAR point clouds into filtered digital elevation models, strip vegetation returns, and generate shapefiles containing basic contour geometries. The mapper then imports those vector layers into their map project as background templates. This multi-step pipeline separates raw terrain analysis from manual symbolisation, requiring separate local software installations, manual coordinate system alignment, and substantial disk space for high-resolution ground models.
How browser-based elevation ingestion handles terrain data
Browser-based ingestion queries pre-indexed elevation tiles directly over network protocols using exact geographical bounding boxes selected on the screen. The browser vector engine extracts elevation matrices for the designated area, calculates terrain contours instantly, and converts the resulting line work into standard orienteering symbols without intermediate file conversions or local storage.
We built Gratic to eliminate the multi-stage manual processing pipeline that traditional desktop workflows demand from sports cartographers. Instead of hunting down national LiDAR tiles on regional portals and loading heavy GeoTIFF files into standalone software, you open a browser tab and drag a rectangle across your target terrain. Gratic maintains elevation tile by tile, allowing the vector engine to fetch the required surface heights immediately for that defined boundary. The system calculates the terrain morphology and writes real contour lines directly onto your drawing canvas. These generated curves conform immediately to standard symbol definitions, allowing you to begin drawing with pens that behave like a cartographer expects.
This browser workflow also unifies height geometry with base terrain features derived from open sources. When you drag your bounding box, the editor imports vector data from each connected national mapping service alongside the elevation tiles. Roads, streams, and contours arrive populated with their appropriate orienteering symbols simultaneously. We publish the data sources we hold tile by tile alongside the licences governing each national service, showing measured reasons if a regional dataset remains blocked. If your project downstream requires desktop refinement, Gratic provides direct export so your files open in OCAD without losing vector fidelity or layer structures.
Comparing digital elevation model ingestion methods
Cartographers select elevation workflows based on data density, required processing steps, and how easily raw heights translate into editable vector lines.
| Elevation data source | Typical input formats | Processing location | Intermediate steps required | Vector output status |
|---|---|---|---|---|
| Raw LiDAR point clouds | LAS, LAZ | Local desktop workstation | Ground classification, rasterisation, noise filtering | Unsymbolised vector polylines |
| Gridded elevation models | GeoTIFF, ASCII XYZ | Local desktop software | Coordinate projection, contour interval calculation | Unstyled raw contours |
| Pre-processed elevation tiles | Web-hosted raster tiles | In-browser vector engine | Bounding box selection in browser tab | Standard ISOM contour symbols |
| Pre-generated shapefiles | SHP, GeoJSON | External GIS desktop package | Polygon clipping, line smoothing, manual tagging | Generic GIS vectors |
When standalone desktop processing remains necessary
Standalone desktop processing remains necessary when mappers conduct fieldwork completely offline without an active internet connection or when projects require non-orienteering GIS capabilities. Desktop packages also allow operators to inspect raw ground-classified LiDAR returns manually to detect subtle historical ruins or micro-features hidden beneath dense forest canopies.
Offline resilience represents a core operational boundary for browser-based mapping tools. If an orienteering surveyor is stationed in a remote mountain hut without reliable internet access, a browser tab cannot fetch fresh elevation tiles or query national mapping service vector data. Under these conditions, a locally installed desktop application reading raw GeoTIFF or LAZ files from an external hard drive is required. The surveyor retains complete control over offline computation, local file caching, and raw point-cloud classification directly on their operating system.
Similarly, municipal planners, civil engineers, and urban utility developers need GIS attribute databases that sit outside the scope of terrain sports. These municipal workflows depend on complex spatial database schemas, topological network validations, and property boundary registers rather than ISOM symbol sets. Gratic targets orienteering, rogaining, and adventure racing competitions where the primary requirement is turning ground terrain into legible competition maps. For traditional GIS tasks lacking orienteering standards, traditional desktop GIS software remains the intended tool.
Frequently asked questions
Can Gratic open existing OCAD files that contain elevation contours?
Yes. Gratic maintains direct compatibility with files that open in OCAD, allowing cartographers to import existing survey sheets, review vector layers, and continue vector drafting in a browser tab without installing desktop software.
How does Gratic sign users in to access map projects?
You sign in with your email address, and a sign-in code arrives in your inbox immediately. You do not need to invent a password, download a desktop client, or manage local license keys across machines.
What happens if a national mapping service restricts vector data exports?
We publish both halves of what Gratic pulls in, documenting elevation data alongside every national mapping service we query. If a national agency restricts access through its licensing terms, we publish the measured licensing reason openly within our catalogue.
Can scanned paper maps be georeferenced alongside imported elevation layers?
Yes. Gratic includes tools to georeference scanned paper maps alongside elevation layers, letting you align historical surveys against modern base vectors and tile-by-tile ground heights inside the same browser session.