MapsMadeEasy
lvl.4
United States
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Background
Drones Made Easy has a special interest in how cameras place geotags into their images. Accurate geotags allow users to build a map that is created from individual aerial images that aligns with the real world. The process of aligning an image to represent space in the real world is called georeferencing.
Geotags are (or should be) the GPS coordinates and altitude of the camera at the exact time when an image is taken. These coordinates are written to the EXIF metadata that is embedded in a JPG image file. Other EXIF tags include exposure time, focus method and make/model of the camera. In general, the majority of cameras are not equipped with a GPS receiver, but almost all cameras write EXIF data embedded in the images they create.
Most of our mapping customers either use cameras that record GPS data (such as the Canon S100) or a GoPro which does not record the GPS data. For the GoPro, creating a georeferenced photo map requires an additional process of associating points in the imagery with points on a basemap or manually entered GPS coordinates. The results from doing this extra step are very accurate, but are sometimes unnecessary if super high accuracy is not required and sufficient geotags exist. For our Maps Made Easy service, this process is fully handled in the user's web browser.
The easiest way to create a georeferenced orthophoto map is to record the GPS data along with the pictures and use that information when stitching everything back together. Given good geotags, our system can give pretty well aligned results (within a few meters) without any extra steps or inputs. For a lot of applications, this is good enough.
Comparisons
Being a DJI dealer, we have a lot of experience using the various DJI multirotors to carry different camera systems for mapping.
The Phantom 2 has an internal GPS and good photogrammetry tools build into the PC Ground Station software but no integrated camera, so without using a datalogger and using the log file to insert the appropriate data into the images, Phantom 2 users were required to manually georeference their images if they were using a camera that could do so on its own. Our Deluxe Mapping Bundle was designed for users that required enough precision that they would be manually georeferencing their images anyway.
When the Vision+ came out, we got excited that its Ground Station software and geotagging camera would provide a great all-in-one platform to collect good mapping data with minimal effort or investment. While it is certainly easy to use, the Vision+ is held back from being a great mapping platform by its fisheye lens and the fact that it doesn't record the altitude (?) made the recording of the GPS coordinates useless for mapping. Not to mention the fact that the GPS coordinates are not recorded with very much precision. The coordinates are recorded as Degrees, Minutes, Seconds with no decimal precision on the Seconds portion. This limits you to 10s of meters of accuracy. The outputs of the Vision+ still require manual georeferencing and quality was limited due to the optics.
The Inspire 1 came out with its flattened lens for the camera and we thought it might be the platform we were looking for. Its imagery turned out to be some of the best mapping imagery we had processed but even though it recorded its altitude accurately in the geotags, it was still limited by the fact that it recorded the GPS coordinate data in the same manner as the Vision+. We don't know why DJI was limiting the accuracy of this measurement, but it was getting pretty annoying.
Finally, the Phantom 3 was released and it turns out it has everything we were looking for. It has a similar distortion-free lens to the Inspire 1, records the altitude information and actually records decimal precision GPS location in the geotag! Hallelujah! We got one of the first batches of the new Phantom 3 and immediately took it out into the field for a couple of test mapping missions. The results have been great.
We think the Phantom 3 is a winning combination of ease of use, optical quality, GPS accuracy and battery life that will make creating quality maps quick and easy.
Here is an example of a Phantom being used to map a 6.5 acre area:
https://www.mapsmadeeasy.com/map ... 4c93580c3acbae9ee9/
Future Development
Drones Made Easy is planning on releasing an iOS application in the coming months that will make the process of collecting quality data with a Phantom 3 as easy as it can possibly get. After collecting this data, the application will be capable of uploading the imagery directly to the Maps Made Easy map processing service for 3D model and orthophoto map processing.
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