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I have found a solution... It was a two step process. First I set the spatial analyst extents to be the same as the larger DEM raster. Then, I created a conditional statement in the raster calculator to only save the cells from the second raster that were greater than the first. Then I used the mosaic to new raster tool to replace the cells in the DEM raster with the levee top raster cells that were higher than the existing DEM.
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11-01-2012
10:53 AM
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I have two raster datasets. The first raster is a very large DEM of a river network at 15.625 ft spacing. The large DEM was generated by resampling roughly 3,000 smaller rasters from a 3.125 ft cellsize to a 15.625 ft cellsize, then mosaicing them all together to form the final merged raster dataset. The issue here is that a critical part of the dataset is the elevation of the levee tops in the system which were degraded slightly in the resampling operation. I have a 3D polyline of the levee centerline alignments that I have sampled elevations from the raw 3.125 ft rasters and converted the vertices to points. Then I converted those points to a 15.625 cellsize raster. The second raster dataset is a breakline of sorts. It would obviously be preferable to use the polyline as a breakline and generate a terrain from the points. However, I do not have the point shapefiles that the raster DEM's were generated from. What I would like to do is somehow use the raster calculator to replace the values of the first DEM with the values of the second DEM of the levee tops, where the two rasters overlap. Is this possible or is there some other work around for my problem. Any suggestions would be appreciated. Thanks!
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10-31-2012
02:50 PM
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Hello, I have 37 very large DEM rasters that I am trying to stitch together using the mosaic to new raster tool in Arc. Each raster has a cellsize of 3.125 by 3.125 ft. There are approximately 25,000 rows and 25,000 columns in each raster and they take up about 2 GB. The issue I'm having is that mosaicing the rasters is taking an extremely long time. Several hours or more just to stitch 2 rasters together and the length of time increases as the extent grows from more rasters being added. I understand this may be the norm for such large datasets, however I am using a top-of-the-line machine to perform these tasks and I am wondering if there is a way to speed things up by altering some settings. Here are my questions. 1) If I change the environment settings to "not generate pyramids" or "not generate statistics" does this increase the speed at which two rasters are mosaiced? 2) Of the many mosaicing tools, which one is the fastest? Is it faster to use mosaic to new raster, or to create an empty raster first and then use one of the other mosaicing tools? 3) Ultimately, once all 37 rasters are mosaiced, the extent will be very large. Is it faster to first generate an empty raster with the same extents as the combined 37 rasters, and fill it with <null> values, then mosaic all the rasters to that dataset? 4) Are there any other tools/settings that will increase mosaic speed without any loss of data resolution? Thanks!
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10-25-2012
04:04 PM
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Thanks for your help, that solves my problem! I followed your step-by-step procedure and it worked perfectly. Thanks again!
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10-17-2012
12:48 PM
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The problem with locating the features along the routes is that there is no XY location data in the text file, so I can't make a shapefile out the information. The only relation the text file has to the alignments is that it gives the river mile stationing of each point along a reach. I have attached an example shapefile and text file. Thanks
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10-17-2012
11:53 AM
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Morning all, I have a fairly complicated linear referencing task that I am trying to tackle with Arc and so far it is stumping me. Basically I have several river alignments that I have converted into routes. Some are short, while others are very long (~100 miles). Separately I have a text file with water surface elevation along each of the river alignments at some arbitrary river mile stationing. The text file stationing does not line up in any way with the vertices of the river alignments (which were exported from CAD). What I am trying to do is somehow create station points at each of the river miles listed in the text file along each alignment in GIS. The goal being to assign water surface elevation to those nodes. The problem would be so much simpler if I had XY locations for each of the water surface elevation points, but unfortunately all I have is stationing relative to each river alignment. Any thoughts or ideas? Edit: Using ArcGIS 9.3 and have licensed version of ET Geowizards Thanks!
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10-17-2012
09:07 AM
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