41,763 reputation
9102177
bio website quantdec.com
location Northeastern US
age 15
visits member for 4 years, 9 months
seen 12 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 I can be reached through (outdated but still valid) links posted on my web site.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.


13h
awarded  Enlightened
1d
comment Why Haversine formula and Web Mercator give different length between two latlng points?
@Mikkel I think that's still a good interpretation. However, the edit shows that a much more egregious issue has to be dealt with first. The discrepancies between an ellipsoidal and spherical calculation will not exceed one part in 300, whereas the reported discrepancy is a 25% difference. Although this apparently is a result of using a Mercator projection, it's not evident how the OP obtained it, so we're waiting for clarification.
1d
comment Why Haversine formula and Web Mercator give different length between two latlng points?
@Mikkel We need to take some care concerning what "based on" means in Google's case, because it actually is a corrupted version of the appropriate procedures. As Wikipedia puts it, "the Web Mercator uses the spherical formulas at all scales whereas large-scale Mercator maps normally use the ellipsoidal form of the projection." It would therefore be reasonable to try to check Google's reported distances by applying spherical formulas--that is, the Haversine or its equivalent. Given the large discrepancy reported in the edit, though, that's a moot point now.
1d
reviewed Reviewed Is it possible to highlight water steam sources on Landsat 7 image?
1d
comment Is it possible to highlight water steam sources on Landsat 7 image?
Could you tell us how you propose using the QB to answer this question?
1d
reviewed No Action Needed Making get feature request to forget between clicks in OpenLayers 3
1d
reviewed No Action Needed How to use KML files with PhotoOverlay in Google Street View?
1d
comment Why Haversine formula and Web Mercator give different length between two latlng points?
@Mikkel Presumably because Google uses a spherical earth model for its "Web Mercator" projection. Even so, your question is pertinent because this thread is wondering about "most accurate measure" of distances, and surely a calculation using an ellipsoidal model will be more accurate than using a spherical model: see gis.stackexchange.com/questions/25494.
1d
comment Display coastline
In ArcMap you can easily generate the elevation=0 contour in many ways. What I am struggling with is that you explicitly reject this natural solution in the question, making it unclear what you really are looking for.
1d
comment Why Haversine formula and Web Mercator give different length between two latlng points?
Clearly those "Google results" are using the Mercator-projected coordinates, which will inflate distances at 37 degrees latitude by 25%. But Google Maps provides various ways of computing distances and some of them--such as its measurement tool--appear to be accurate. Exactly how are you using Google Maps to obtain these distances?
2d
comment Display coastline
So what you seem to mean is that the coastline is where zero values ought to be, but (due to the discreteness of the representation) it cannot accurately be found by selecting cells with values exactly zero. That's understandable--it's a common problem--but it does not explain why you rule out computing the zero elevation contour.
2d
reviewed Close how to export feature classes from geodatabase
2d
reviewed No Action Needed Postgis 4D Range Query
2d
reviewed Leave Closed Generate a series for each Survey_ID based on chainage sequence
2d
comment Display coastline
Does that legend imply the coastline should be found at all zero values? Although it would seem to, that appears to contradict your statement about the zero elevation contour. How do you reconcile that?
2d
comment Display coastline
How, exactly, do the colors you display represent values in the raster?
2d
reviewed Looks OK What is the difference between DEM, DSM and DTM?
2d
comment What is the difference between DEM, DSM and DTM?
Welcome to our site. You might want to visit our help center so that you can better understand what kinds of answers are sought here.
2d
comment Strange spatial interpolation results from ordinary kriging
I would suggest taking a different approach, one that has some valid statistical theory to support it: when you have different kinds of measurement, it is rarely appropriate or effective to lump them together into the same dataset. Instead, consider regression-based approaches or even cokriging.
2d
comment Strange spatial interpolation results from ordinary kriging
If you restrict the analysis to areas outside Region X, the variogram should change dramatically: in particular, its range should lengthen. If all you want is "eye-pleasing results," then you shouldn't be using a complicated, computing-intensive method like kriging. Consider a smoothing spline instead.