41,129 reputation
9100178
bio website quantdec.com
location Northeastern US
age 15
visits member for 4 years, 8 months
seen 17 hours ago

Consultant (environmental and spatial stats a specialty), expert witness, and teacher. I can be reached through (outdated but still valid) links posted on my web site.

Twitter: @WilliamAHuber // ASA-P website: http://amstatphilly.org/


Why waste time learning, when ignorance is instantaneous?

--T(iger) Hobbes.

For any complex problem there is a simple solution. And it's always wrong.

--[Mis?]attributed to H.L. Mencken by Dava Sobel, Longitude.


17h
comment Determine value nearest to given coordinates
There are many possible valid answers, including "just look at it." Could you please help us out by editing this question to stipulate (a) how you want to supply the (x,y) input, (b) whether this is a one-time-only operation or needs to be applied to many coordinates, (c) what format you want the output in, (d) whether you want just to look up a cell value or if you want to interpolate among values in the raster, and (e) what raster-oriented extensions to ArcGIS you have access to.
17h
reviewed Close what is the shape of the data that saved in GIS files ?
17h
reviewed Leave Closed How to contact the author of a CartoDB map
1d
comment How can I calculate the vertical distance to the nearest water?
@BlindJesse has a good solution if "nearest" truly means that, rather than strictly downstream to the nearest water. It's a simple workflow: attribute the water grid with the elevations. Round them to whole numbers so you can apply Euclidean allocation. Subtract the DEM from that, then take the absolute value of that difference. Done.
2d
comment If I were flying over a flat world at constant elevation, taking aerial photos, how would I patch them into a mosaic?
Whether you believe I understood or not, your claims are mathematically wrong whenever the world is not flat. In fact, the errors that your method will produce can be used to measure curvature.
2d
comment Term for combined Raster and Vector data
I have created such datasets to expedite certain kinds of cost-distance analyses. My term for them is "hybrid (raster-vector)" datasets. In addition to having raster and vector components, they also contain explicit links between the two.
2d
reviewed No Action Needed Calculate geometry on some features have same X and Y for start and end?
2d
reviewed Reviewed Need statistics from US census
2d
comment Need statistics from US census
I'm voting to close this question as off-topic because it does not appear to be about GIS at all.
2d
reviewed Leave Open What are the skills a GIS Expert needs to have?
Apr
14
comment Clarification on a previous Utilization Distribution Overlap Index (UDOI) answer
I have fixed the typo in the link and have clarified point (3). (I appreciate you calling attention to that ambiguity.) The values you get for the zonal sums will depend on the units you use. For instance, in my example the values would be many of orders of magnitude different if I had used densities per square meter rather than densities per square kilometer. The vertical axes in my illustrations should make it clear that 0.1838 is a reasonable value in this case: you should take a similar look at your datasets to decide whether 9000 is reasonable.
Apr
14
revised How to Calculate Utilization Distribution Overlap Index (UDOI) in ArcGIS Desktop?
added 20 characters in body
Apr
14
comment How to compute the number of none NA-values for each row?
Good points. There is both a pedagogical and a conceptual point to the rowSums solution in this case, though: the opportunities to capitalize on the type-punning that equates TRUE with 1 and FALSE with 0 are numerous and frequently overlooked. Here it amounts to the difference between counting objects (length(x[is.na(x)]))) and summing indicator functions (rowSums(!is.na(r)))).
Apr
14
awarded  Necromancer
Apr
14
revised Kernel Density with population
rolled back to a previous revision
Apr
14
comment How to compute the number of none NA-values for each row?
It's much faster (and even a little simpler) to use something like rowSums(!is.na(r)).
Apr
14
reviewed Close Best map opensource map server for dynamic map
Apr
14
reviewed Close Software development and cartography
Apr
14
comment What's the best neighborhood size to smooth the ASTER GDEM v2, resampled at 1m res, in GRASS with r.neighbors?
How much would be "too much"? The answer depends on your application, so perhaps you could say a little bit about that in an edit to this post.
Apr
14
comment Kernel density raster - convert to real world values?
This question gets asked a lot, so I think you might be able to dig up some answers here without much trouble. For instance, I found gis.stackexchange.com/questions/14374 by searching on kernel density units‌​, and I see several more potentially useful hits on that page of results. Check them out!