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Is there a way to find a point with highest elevation in specified area by using ArcObjects? Let's say that I have a raster with DEM and I would like to establish some areas of interest in this raster. In each AOI, I would need to find a point where terrain has the highest elevation and return coordinates of this point.

I looked into ArcObjects API and I found only a manual way to discover such point, that is:

  1. Establish AOIs
  2. For each AOI, find corresponding pixels in the raster
  3. Having sets of pixels defined for AOIs, iterate over each set and return a point with highest elevation

This process is doable but absolutely impractical due to performance concerns.

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    Why not work with the grain instead of against it -- mask the elevation grid with the AOI, then build statistics to identify the maximum value (there might be multiple pixels with that value), use "Equal to" to null all but the maximum, then convert to point(s). Much like this – Vince Dec 8 '15 at 16:43
  • Thanks for the tip! So I masked the grid with AOI and calculated statistics for it - I have the maximum value identified. I assume that using "Equal to" will produce a raster having the sole point(s) that have values equal to maximum that was identified. Having such raster, how can I convert its data to points? Could you please elaborate? – Konrad Dec 9 '15 at 0:29
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    Just as the linked answer states, convert raster to point. I found this link by pasting that expression in the desktop.arcgis.com help system search engine. – Vince Dec 9 '15 at 0:37
  • Thank you very much Vince, I succesfully got my highest elevation point. This may seem easy, but ArcObjects are pretty cryptic for newcomers. I will post a detailed "how-to" answer to my question. – Konrad Dec 11 '15 at 10:39
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    You really need to know ArcGIS before attempting ArcObjects (which is cryptic and mind-boggling, even for experts) – Vince Dec 11 '15 at 11:45
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Thanks to Vince's comments I was able to perform succesfully the whole process.

As I wrote, first I wanted to establish a number of AOIs on the raster. Nothing fancy here, I got raster properties by using this small function below:

public static IRasterProps GetRasterProperties(IRasterDataset rasterDataset, int rasterBandIndex)
{
     IRasterBandCollection rasterBands = (IRasterBandCollection)rasterDataset;
     var rasterBand = rasterBands.Item(rasterBandIndex);
     return (IRasterProps)rasterBand;
}

Given the raster properties, I created a number of areas each defined by an IEnvelope. In order to split the input raster to AOIs, I used the ExtractByRectangle Geoprocessing tool.

ExtractByRectangle extract = new ExtractByRectangle(inputRaster, envelope, path);
IGeoProcessorResult2 result = gp.Execute(extract, null) as IGeoProcessorResult2;

parameters:
inputRaster - IRasterDataset (input raster)
envelope - IEnvelope (definition of our AOI)
path - file path to resulting raster

I won't describe all Geoprocessing shenanigans, but that is where ArcObjects get very cryptic in my opinion. A number of error codes that have no obvious explanation doesn't help too. I found great code by Kirk Kuykendall that helps a lot with debugging here: Avoiding fails from ArcObjects geoprocessing with .NET?

Now, we have our small raster AOIs. I need to get the point of maximal elevation for each of them. Hence, I start with computing statistics for every AOI using the function below:

public void ComputeRasterStatistics(IRasterDataset rasterDataset, int rasterBandIndex)
{
     IRasterBandCollection rasterBands = (IRasterBandCollection)rasterDataset;
     var rasterBand = rasterBands.Item(rasterBandIndex);
     RasterStatistics = rasterBand.Statistics;
}

Statistics deliver information concerning values of raster extremes, inclusing the maximum point value of a raster. Next I convert the raster to points using the function below.

public static IFeatureClass RasterToPoints(IRasterDataset raster)
{
     IConversionOp conversionOp = new RasterConversionOpClass();
     IWorkspace shapeWS = FeatureWorkspaceHelper.CreateInMemoryWorkspace();
     var featClass = conversionOp.RasterDataToPointFeatureData((IGeoDataset)raster, shapeWS, Guid.NewGuid().ToString());
     return (IFeatureClass)featClass;
}

FeatureWorkspaceHelper.CreateInMemoryWorkspace(); is a helper function of mine, that creates an empty in-memory workspace. Have in mind this can be obviously done with 'classic' file workspace too.

Now I just need to find a point that has the maximal elevation and return it. The function below (some hardcodes there!) does that.

private IPoint GetRasterMaxElevationPoint(IFeatureClass featureClass, double val, int elevationIndex)
{
    IQueryFilter queryFilter=new QueryFilterClass();
    queryFilter.WhereClause = "GRID_CODE >= " + (val - 0.01).ToString();

    var cursor = featureClass.Search(queryFilter, true);
    IFeature feature = null;
    IGeometry shape = null;
    double maxValue = double.MinValue;
    while ((feature = cursor.NextFeature()) != null)
    {
        if ((double) feature.Value[elevationIndex] > maxValue)
        {
            shape = feature.Shape;
            maxValue = (double) feature.Value[elevationIndex];
        }
    }

    return new PointClass()
    {
        X = shape.Envelope.LowerLeft.X,
        Y = shape.Envelope.LowerLeft.Y,
        SpatialReference = shape.SpatialReference
    };
}
0

You can generate a digital elevation model online based a location point and perimeter (i.e. Radius). The algorithm then finds the highest elevations within. https://www.mymountain.xyz - accounts are free. Asheville, NC with large radius]1

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