Supporting a set of humanitarian field experiments in Camp Roberts
GISCorps volunteer, Yamini Manickam, supported a set of humanitarian field experiments in Camp Roberts, California on August 15th. Yamini is a GIS professional from California and has expertise in remote sensing. Her main tasks consisted of processing the imagery generated from several planes on the same day as those images were captured. The process included: geo rectification, edge matching and mosaicking those imagery. She wrote the following report shortly after the event.
The purpose of this experiment is to determine how first responders can utilize aerial imagery taken during or after a disaster in order to provide appropriate assistance. During the experimentation, aerial oblique images were taken by the Civil Air Patrol at elevations of 2000, 4000, 6000, 8000 and 10,000 feet using a Nikon D90 camera. These geotagged images were later georeferenced and the amount of time taken to georeference the images were monitored.
The georeferencing process discussed in this report was performed using the ArcGIS Desktop 10.1 trial version. The trial versions are free and are valid for 60 days. In addition to the trial versions, Esri, the company that makes ArcGIS Desktop 10.1 also provides free software for disaster response.
1. Open ArcMap.
2. Add a georeferenced image such as the Bing Aerial basemap.
3. Enable the “Georeferencing” toolbar.
4. Add the non-georeferenced geotagged photo. Click on the “Fit to Display” command in the Georeferencing toolbar menu.
5. Using the “Geotagged photos to points” tool, create a point for the location where the photo was taken. This will be helpful in locating the photo spatially before beginning the georeferencing process.
6. Compare the basemap and the photo and add control points using the tools in the Georeferencing toolbar. For more information on how to perform georeferencing in ArcGIS, please see http://resources.arcgis.com/en/help/main/10.1/index.html#//009t000000mp000000.
Repeat steps 1 through 6 and perform the georeferencing using the Auto Registration tool.
Figure 1 – Manual rectification with 17 control points
Figure 2 – Rectification using Auto Registration
It was observed that manual rectification yielded good results compared to auto registration (Figure 1). Also, the more the control points, the more accurate the quality of the georeferencing was. The time it took to complete the manual georeferencing in Figure 1 was approximately 15 minutes whereas the auto registration tool took less than a minute. Depending on the time constraint, the first responders can choose how many control points to add starting from the corner of the image and going towards the center.