Hi Tad,
I'd say you should save your data in a local projection first. Then you
can use meters as units which will make more sense than 0.000000001
degrees or whatever.
I tried 10 meters in epsg:3857 and it worked out well.
Good luck,
Raymond
On 08-01-18 18:26, Tad Deshler wrote:
I have created a vector layer from a spreadsheet that contains water
depths and x-y coordinates in latitude and longitude (276 points in all,
see attached). I've used the Interpolation plugin to create a TIN of
water depths, but the interpolation doesn't cover the same region as the
underlying points (see attached graphic). The results I do get seem
accurate (deeper red points are at southern edge of grid), but are only
partially what I need.
After specifying the interpolation attribute (Depth), the output section
of the interpolation plugin displays the default number of columns and
rows (300 for each). The Cellsize X is specified as 0.00001 (I think
because my longitude data is to five decimal places). So I left number
of columns and Cellsize X as 300 and 0.00001, respectively. The number
of rows is also specified as 300, but the Cellsize Y was initially
specified as 0.00000, which not surprisingly yielded nothing for the
interpolation. So next time, I changed the Cellsize Y value to 0.00001
to match Cellsize X. This automatically changed the number of rows to
139. Could this be because the spread of my data is from 61.1201 to
61.1215 degrees North, which would be 140 times 0.00001?
I'm using QGIS 2.18.11. I am confused about why the interpolation
doesn't cover all the sample points. I have tried changing the values
for X and Y min and max (making them larger than the actual data range),
but this only serves to place the interpolated result OUTSIDE the sample
points, so I don't think that is the solution either.
Can anybody provide some guidance on where I'm going wrong here?
*Tad Deshler*
Coho Environmental LLC
206.778.9274
tad.desh...@cohoenvironmental.com
<mailto:tad.desh...@cohoenvironmental.com>//
cohoenvironmental.com
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