Workshop 4: Stitching Images Into Maps
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.
- Activity 1: Sorting your images (1 hour)
- Activity 2: Building your map (2 hours)
- Activity 3: Posting or exporting your map (30 min)
Supplies you will need:
- One computer and one mapping data set for every 2-3 people
- SD card reader
- HINT: It is easiest to use a computer with a mouse.
- HINT: Some people find it helpful to use a projector and a screen to enlarge their map as they build it.
Activity 1: Sorting your images
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.
- The easiest way is to go through all your images and cull out the best 30 or so that show the geographically diverse areas of your site. (Recommended)
- Here are suggestions for windows or for macs while you go through photos that you'd like to use for your site.
- Other people have used file size to help them sort images.
- You can choose not to sort and find a good photo to use as your base and build your map from there.
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.
Note on Infragram images:
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.
Activity 2: Building your map
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:
- Name your map
- Identify the location (address or coordinates)
- Give a description. Suggested comments include: the date the images were captured, weather that day, who mapped the site and why you were interested in collecting the data. This information can be edited later.
Uploading your images into Mapknitter:
- Start with uploading your base image and upload it into Mapknitter by dragging it onto the map or clicking
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
- Distort the image with
- Rotate images using the
- Toggle "outline mode" with the
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.
- Repeat steps 2-4 until your map is complete and shows all of the site you were hoping to map.
- Once your map is complete you can annotate it using the annotate toolbar.
Activity 3: Posting or exporting your map
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!