Workshop 4: Stitching Images Into Maps
Once you have collected your images, you shoul...
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Once you have collected your images, you should set aside a block of time (at least 3 hours) to sort through them and stitch them into a map. It is best to do this as close to the time that you collected them as possible (within the next 3 days) so you remember features you saw from ground level -- this'll help you figure out where the photos correspond to!
You can build your map using Public Lab's open source MapKnitter.org. You can use the same login that you do with your Public Lab account.
Create a folder on your desktop to upload all your photos into. From here you will sort out good images to use in your map. This is because it is easier to building a map from a small set of good images than from the entire set of images you collected mapping.
There are many ways to sort your images.
Once you have gone through your images, pick one that has a clear, distinguishable feature that you will be able to build your map off of. We call this your "base image," and suggest you rename it as such.
If you are using images from a GoPro (or GoPro-like camera), a Mobius Action Cam, or an Infragram Point and Shoot camera, your images will be distorted by a fish eye lens. They will need to be corrected before you can stitch them in Mapknitter. One way to do this is by using the open source program called GIMP. Here are some directions on how you can do this, and here's a prototype web-based version that we hope will make this easier.
To learn the basics of map stitching, the video on the front of MapKnitter.org offers a quick introduction.
Once you have logged on to MapKnitter, there is a column on the right hand site where you can build a map. This will ask you to:
Uploading your images into Mapknitter:
Place your image over the map so it aligns as closely as it can with the base images. Helpful features in the toolbar include:
Toggle transparency with the t key
Lock images with l (once your images are where they fit best)
Once your base image is set and locked, upload another image that shows a part of your site that abuts the base image. They should overlap slightly.
Writing a research note is a great way to share your work. The tab on MapKnitter entitled "Post" will bring you to a page where you can write a research note on PublicLab.org. To embed your map in the note, go to the "About" tab on Mapknitter, click the "embed code" button and copy/paste it in your research note. MapKnitter maps can also be shared via URL or embedded into blog posts or other web pages.
Exporting your map
(optional) Sometimes you need to print a map out. Exporting your map allows you to download it in different formats, often for printing. You can download your map in many formats (JPG, Geo-TIFF, Tiled Map Service, OSM-style, etc.).
When you've finished working on your map, click the export button. Exporting can take some time. If it takes longer than 2 hours, we suggest you check the advanced options tab and reduce the resolution of your map and try to export it again.
Let the community know what you're mapping on the mailing lists!
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