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Part of the Grassroots Mapping Curriculum series.

Creating a map from a set of aerial photos

Learn to turn aerial images into maps with the Public laboratory's open source tool. Upload an image, rotate, distort and stretch it onto a reference map, and use the transparency and outline modes to check how close the fit is. Then export to GeoTiff or OpenLayers/TMS.

MapKnitter ( is a free and open source tool for combining and positioning images (often from in geographic space into a composite image map. Known as “orthorectification” or “georectification” to geographers, this step covers the process of figuring out where images can be placed on an existing map, and how they can be combined, or “stitched” together. You are likely to have many images of overlapping or identical areas, which is why MapMill or some type of sorting is used to determine which source images to use from the original set. 


MapKnitter can make maps from any image source, but it particularly lends itself to making maps with balloons and kites. The manual process of making maps with MapKnitter differs greatly from automated aerial imaging systems. In those systems the imaging is of a higher precision and processed with spatial and telemetry data collected along with the imagery, typically at higher altitudes and with consistent image overlap in the flight path sequence.

With MapKnitter the cartographer dynamically places each image and selects which images to include in the mosaic. Although the approaches are similar in that they use some type of additional information (usually pre-existing imagery of a lower resolution) as a reference, and that they are bound to specific cartographic elements such as map scale and map projection.


Learn more about MapKnitter in this list of guides:


Upcoming tutorials

  • Photoshop tutorials:
    • Choosing a resolution
    • Importing a base layer from google maps or another source
    • Warping a difficult image with the mesh "warp" tool
    • Turning a Photoshop-produced map into a GeoTiff using MapKnitter


Title Author Updated Likes Comments
Is there a file size limit to the image that can be uploaded? @calmstrong almost 2 years ago 0
Intermittent issues logging into MapKnitter @warren over 2 years ago 0
mapknitter, downloading, exporting @pataxte about 4 years ago 2
How to save and return to a map, and uploaded images in Mapknitter @pataxte over 4 years ago 3
MapKnitter map of Garbage Hot spots @silentsairam over 4 years ago 1
Can geotagged aerial images be automatically placed in the right location on the map according to their coordinates? @se18023 over 4 years ago 6
Mini video recorder @Ag8n over 5 years ago 4
Geotiff error when trying to export @Zemans over 5 years ago 9
How to choose the order of pictures when exporting @adyr_construction almost 6 years ago 4
How do i overlay a north to south aerial image on a digital map? @yuvalsh almost 6 years ago 4
Is there an offline version of Mapknitter? @stevie about 6 years ago 1
Problem with rotating the image @narendradesilva over 6 years ago 2
User Interface on Mac @mlapey over 6 years ago 2
please help! @ROCKETMAN almost 7 years ago 1
how do i get my old map @jgee7 almost 7 years ago 0