The need for assigning accuracy
We are seeing observations with a range of locational accuracy, a measurement of the location’s precision. Some people are posting observations from with very general locations (over 1 km), while others are posting observations that are mapped to within 5 or 10 meters of the actual observation. No matter what your accuracy is for an observation, it is important to assign the accuracy so we know how the data can be used. An observation lacking an assigned accuracy has very limited value.
The observations that you provide are used for a variety of conservation purposes. Some do not require a high degree of accuracy, like county lists. Other projects, like distribution modeling, require an accuracy of 30 meters or less. Observations without an assigned accuracy will not be used for environmental review, conservation planning, or distribution modeling.
Fortunately, it is easy to assign accuracy with iNaturalist. If you record the location with the iNaturalist app, then it assigns the accuracy automatically. However, if you assign the location using the metadata from a photo, or by manually mapping it through the web interface, then you need to add the accuracy by editing the observation.
The accuracy field, labeled “Acc (M)”, is located directly below the coordinates, and just above the map. Just enter the distance in meters that includes the entire area where the observation could have taken place. When you assign accuracy, a red circle around the point will appear. You can click on the circle and drag it in or out based on the map and it will automatically adjust the accuracy. It is also possible to edit accuracy for multiple observations using the batch edit tool.
If you are concerned about mapping a precise location, you may want to adjust the geoprivacy setting. You can learn more about geoprivacy here: http://www.inaturalist.org/pages/help#geoprivacy
Comments
Thanks Cullen, I was not aware of the importance of this attribute. I plan on adding it to my past observations, but first I'd like to share my thoughts about assigning accuracy to my observations which might help others.
Most of my observations are created from geo-tagged photos on Flickr. I'm pretty confident that the accuracy of the coordinates embedded in the photos is 5-10 meters. (I use a dedicated GPS logger and software that matches the logger's coordinates with the timestamps on my photos.) But these coordinates represent where I was standing -- not where the animal I photographed was. So I need to estimate how far away the animal I photographed was, and use that plus 10 meters as the radius of the circle of accuracy.
For example, if I photographed a deer from 20 meters away, and figure the accuracy of my location is within 10 meters, then the accuracy of the observation should probably be 10 + (20 * 2) = 50 meters.
Does this make sense? Am I over-thinking it? :)
Yes, that is correct, or you could just move the point to where the deer was and estimate your accuracy.
When doing surveys I have used a compass bearing and an estimated distance to assign a point based on my GPS point. With iNaturalist, you are unlikely to be that far from the animal when you photograph them, but you do want to include that. Sound recordings might add even more spatial uncertainty.
Sometimes it seems unnecessary to differentiate a few meters, but it can make a difference when you are using data for habitat modelling. Of course, the most important thing is to be able to differentiate precise points from very general localities.
Thanks for commenting Mikael. By the way, Jonah pointed out a great app for geotagging photos (GeotagPhotos); it has really helped my photo management. We will have a journal post about it soon.
-Cullen
The GeotagPhotos iPhone app looks pretty slick! Thanks for passing that on. It looks like it's essentially using the iPhone as a GPS logger and streamlining the steps to get your tracks off the phone. But keep these caveats in mind if you're using an iPhone or other smartphone as your GPS logger:
Sometimes smartphones record coordinates derived from cell phone tower proximity or nearby wi-fi networks because it's faster and uses less energy than waiting for the true GPS coordinates. These are often much less accurate. On the iPhone, I know that apps can be written to only use coordinates actually obtained from the actual GPS chip, but not all apps do.
Logging your path with a smartphone can use up its battery relatively quickly. If you plan on using it for all-day or even half-day hikes you might consider getting an external battery.
By the way, for using your iPhone (or iPad or Android device) as a more full-featured GPS unit, check out Gaia GPS:
http://www.gaiagps.com/
Yes, I often use gaiagps on my phone and my ipad since it allows you to download topomaps and aerial imagery for later use when you don't have reception. So far, I have found the GeoTag Photos app to be very precise, but I am checking my observations to be sure. I have the app set to take a point every 10 meters. I have to go back and add accuracy with a batch edit.
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