Change Analysis: Shift Error in Map Projection

Section for FAQs for i-Tree Canopy

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Change Analysis: Shift Error in Map Projection

Post by rdelsack » Thu Jan 26, 2023 6:00 pm

After placing 300 of my iTree Canopy points onto Google Earth Pro, there is a slight skew in positional accuracy among the two map projections. Are there any known solutions to correcting the alignment of the iTree map projection and the Google Earth Pro map projection?
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Re: Change Analysis: Shift Error in Map Projection

Post by Jason.Henning » Fri Jan 27, 2023 11:46 am

Unfortunately, we don't control the projection or alignment of the images within i-Tree Canopy. i-Tree Canopy is displaying the latest images that Google provides through their API. You will notice that lack of alignment even within Google Earth pro images will have different levels alignment over time. This is an issue with all aerial and satellite imagery and is typically due to parallax, or the angle from the camera to the ground. To minimize any errors in your change assessment we recommend focusing on making sure that you are analyzing the same exact point on the ground in both images. For example, if the point appears right on the edge of a road in your original i-Tree Canopy survey you will want to make sure you are judging that same point in the Google Earth change survey regardless of where exactly the point appears on the Google Earth image. In the vast majority of cases these small positional changes don't make much difference but you will want to be very careful with the points that are indeed changing in canopy cover between the two images.
Thanks for your interest in i-Tree.
A member of the i-Tree Team
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