Raster and imagery

Add satellite imagery, aerial photos, and other raster data to your Felt maps.

Felt can read raster data like aerial and satellite imagery, Digital Elevation Models (DEMs), surface temperature measurements and more in a variety of formats.

Static files

Supported file formats

• GeoTIFFs (.tif, .tiff)

• Raster Geopackages (.gpkg)

• ASCII grids (.asc, .xyz)

• Common image formats like PNG and JPEG if an auxiliary World File (.wld, .pnw, .jpw, etc) is provided.

Unknown projections

Most raster formats include relevant information about the Coordinate Reference System the data is in. However, if no such metadata is found, Felt will assume coordinates to be in latitude & longitude (when inside bounds) or Webmercator meters.

Processing

For adequate display, Felt will convert the source data to PNGs with values fitted to the 0-255 range. This might mean some colors may appear slightly different from the original data.

Color tables (paletted values) and No Data values will be respected if present.

Tile URLs

Felt can also read raster data from tiled URL sources in formats like WMTS and XYZ (slippy maps). In Click on Upload Anything in the toolbar and choose the option Add from URL...

These sources must be imported as template URLs, which means the URL must contain the following parts: {z} (zoom), {x} (row) and {y} (column). Instead of the {y} parameter, {-y} may also be used to indicate that tiles are served in TMS format. They must also end in .png, .jpg or .jpeg.

Here’s an example raster URL of the city of Aberdeen from the National Library of Scotland:

https://geo.nls.uk/maps/towns/aberdeen/{z}/{x}/{-y}.png

Example: David Rumsey Maps

Working with the David Rumsey map collection in Felt is easy via our XYZ (slippy maps) tile URL service. Here’s how to get these maps into Felt.

1. Use this map to find maps from the collection that are georeferenced. Alternatively, skip down a few steps if you are already on a map’s metadata page.Once you have found a map, click on its pin, and then its image from the popup:

2. The map will open in another viewer, click on the option “What’s next?” in the bottom right hand corner of the map:

3. This will take you to the map’s metadata page. From here, copy the XYZ link in the “Use in GIS apps” portion of the page

   • for example, the Denver map link is https://maps.georeferencer.com/georeferences/cbbf9f5f-a294-59c9-a2de-88855513599e/2017-03-29T03:45:12.290249Z/map/{z}/{x}/{y}.png?key=SsmpU2nwmUdxCLg5XZaZ

   • once you have copied the link, use command + v to paste it directly on a Felt map. You will notice the toast “Adding raster layer” in the top portion of the map:

     Screen Recording 2023-05-08 at 9.51.57 AM.mov

   • once the raster layer is loaded, you’ll see it as a Layer in your map and you can use the option “Zoom to fit” to zoom to its extent:

Styling raster layers

You can control the opacity, legend and position of a raster layer relative to the basemap in the Style Editor. Learn more about styling raster data.