Steve,
> additional processing steps they can. How does adding code to gdal work?
Just from an observer perspective, it seems that once you have your
additions worked out, attach a diff on on trac ticket. The details
for how to do that are: sign up for an osgeo userid,
http://www.osgeo.org/osge
>
> Steve, there are more things I do not understand either. What is
> 'psData->scale'? Is it the grid cell size?
> So, if 'pafLocalMin' is on one of the 4 corners the distance is not cell
> size (let's call it DX) but instead sqrt(DX*DX + DX*DX).
> And what if data is in geogs? Than DX is clearly
On 16-12-2011 03:31, Stephen Mather wrote:
Hmm. I don't follow? The revision would be this:
float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData)
{
// Hydrologic Slope is the max
// local slope btw center cell and adjacent cells
const double radiansToDegrees
Hmm. I don't follow? The revision would be this:
float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData)
{
// Hydrologic Slope is the max
// local slope btw center cell and adjacent cells
const double radiansToDegrees = 180.0 / M_PI;
GDALSlopeAlgData* psData
float pafLocalMin = afWin[0];
float pafLocalMax = afWin[0];
for ( int k = 1; k < 9; k++)
{
if (afWin[k] < pafLocalMin)
{
pafLocalMin=afWin[k];
}
if (afWin[k] > pafLocalMax)
{
pafLocalMax=afWin[k];
}
Here's what I've settled on. Let me know your thoughts. The algorithm now
correctly calculates angle to lowest nearby point. If it's a local minima,
it instead calculates angle to the nearest high point, which will be a
negative number, so if the user wants to nullify these or use them in
additi
I agree both have their place. Sometimes we get a more consistent or more
interesting answer from our analyses than from our field measurements.
As to the approach, I agree with your assessment, I was thinking
backwards-- one caveat-- how best to handle local minima? Insert a null?
I'm afraid I
Stephen,
It'd be great to see local hydrologic slope in gdaldem.
I've seen a similar discrepancy between "field" slope and most
GIS-derived slopes. The local max hydrologic slope seems to correspond
much better to our perceived slope on the ground. The integrated slope
used in most GIS, however,
Apologies for the flurry, one more change:
float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData)
{
// Hydrologic Slope is the max
// local slope btw center cell and adjacent cells
const double radiansToDegrees = 180.0 / M_PI;
GDALSlopeAlgData* psData = (GDALS
I already see a flaw-- the function should be more like:
float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData)
{
// Hydrologic Slope is the max
// local slope btw center cell and adjacent cells
const double radiansToDegrees = 180.0 / M_PI;
GDALSlopeAlgData* p
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