Tag Archives: Geoprocessing
My name is Andrew–you can call me Drew–and I’m a Desktop Support Analyst with Esri Support Services. If you’ve ever called us to talk about a Python issue, you’ve probably spoken to me! I get a lot of positive feedback from the people I speak with about troubleshooting Python scripts, and I’d like to share the most popular advice I have to give. Whether you’re learning to code for the first time, or just getting started with the ArcPy site package, these tips and tricks should help you get your script back on track and closer to completion. Continue reading
Using Model Builder? Looking for some quick troubleshooting tips? Try these in the order they’re listed below. You can use these to document the steps you take, and if a tech support call becomes necessary, you’ll have a better understanding of what may or may not be causing the problem.
1. Isolate the Geoprocessing tool you believe to be causing the error.
- Run the stand-alone tool outside the model. Does it work with the same inputs and outputs?
2. Isolate a section of the model that is causing the error.
- Create a new model and rebuild the troublesome section to determine if isolating a string of processes helps clarify the issue being faced. Continue reading
With the release of 10.2 and plans to deprecate the ArcSDE command line tools, you may be wondering how current tasks that use these tools can be completed elsewhere. I wanted to share some workflows that have alternate user interface … Continue reading
Lidar data is become increasingly available and there are likewise new tools to analyze and display the data. LAS is the public file format for the interchange of three dimensional point cloud data between data users. LAS information can be … Continue reading
How to add different-sized rasters with NoData Values
One of the most common forum topics is on how to add two rasters with different spatial extents and get a result more than just where the two rasters overlap. Well, the reason the result is only those areas has to do with null values.
There are environment variables to modify to ensure that the rasters line up (snap raster) and the extent is preserved during the process (Spatial Extent). Fixing the environment setting alone will still not fix the output of the process. If you modify the spatial extent to match the “union of inputs”, the output raster will have the correct spatial extent, but the only values will be the values where the two rasters overlapped. So what is going wrong?
Obviously it is the pixel values … or, wait, I guess it isn’t that obvious. Try this piece of wisdom provided by forum poster and Product Engineer, Eric R.
Pixel value + NoData Pixel = NoData Pixel
Pixel value + 0 = Pixel value
Pixel value + Nothing (because your extents are different) = Nothing.
You may be asking, “What is actually happening? Are the values being used in the analysis or not?” Well, the answer is they will be as long as part of that equation doesn’t include a null value. If there is a null value present that will make the output null, then the output will not be correct.
The next question is how to fix it. Bear in mind, both solutions require you to make the rasters that are being used as the inputs match in spatial extent, pixel registration and cell size. You can use the Copy Raster tool and set the appropriate environment settings to accomplish this. Once you have corrected the rasters, then there are two options depending on the desired output,
1. Set the NoData values to a value of zero, so that when they’re added together, the output will have the correct spatial extent and values from both rasters.
Con(IsNull(“RasterSMALL”),”RasterBIG, (“RasterSMALL” + “RasterBIG”))
To recap, there are options to handle the NoData cells. Depending on what output you’re trying achieve, there are different techniques. It’s also important to understand the effect that NoData has when used in raster calculation.
There is a related forum post that discusses using Python to sum multiple rasters together: Calculate sum of 2334 raster layers.
Jeff S. - Geodata Raster Support Analyst
Many of the menus and processes, such as the new geoprocessing toolset for example, have changed in ArcGIS 10.0. One of the biggest changes in ArcGIS 10.0 is the switch from Image Server to Mosaic Datasets.
Previously, in Image Server, you could use the Advanced menu to manually control the options when adding rasters to an image service.
However, there are several situations where rasters added to an ISDEF should not apply the internal overviews that are present with some raster formats. SIDs, and other rasters with multiple levels of pyramids, can affect the performance of image services. Since image services use overviews to increase performance, increasing the number of overviews will improve the performance.
When SIDs are added to an image service with the Advanced process under the General Tab, there is an option to “Include internal overviews”. If this option is unchecked the raster will be added without bringing in the pyramids that are in the raster. For highly compressed rasters like SIDs, there can be many levels of overviews built into the raster which affects the number of overviews created by the mosaic dataset or ISDEF.
In order to replicate the same workflow in ArcGIS 10.0, the Add Rasters To Mosaic Dataset tool includes a section of Raster Pyramid Options. In order to prevent the internal pyramids from being added to the mosaic dataset, set the value to zero (0). This increases the number of overviews that will need to be created, but the performance should be improved. If this option is not used, the overviews that are inherent with the SID will be used in place of overviews. So, the choice from a design perspective is whether to utilize the overviews of the rasters added to the mosaic dataset or to create new overviews for the mosaic dataset. This pyramid option is available for all raster formats, not just SIDs.
To recap, the ability to apply or ignore the internal pyramids and pyramids of input rasters is available in the Raster Pyramid Options section of the Add Raster to Mosaic Dataset tool.
Jeff S. - Geodata Raster Support Analyst
As you may already know, ArcScripts has been closed for adding new scripts. It was a valuable resource for sharing your tools with the community, but there is the new and improved Geoprocessing Model and Script Tool Gallery.
Whether or not you took advantage of ArcScripts in the past, now is the time to jump head-first into the new gallery. Spend some time browsing the tools that are available. Download and rate the tools, submit comments about the tools, and share the tools with your friends via social media.
This resource wouldn’t be possible without the ArcGIS community. Since you’re reading this blog, you’re part of this community. It’s people like you taking the time to share resources that make this gallery so valuable.
So, take a moment and think about the models you have built and the scripts you have written. Would others in this community find these same tools useful for their workflows? If so, consider uploading them to the Geoprocessing Model and Script Tool Gallery. The process is simple and can be done in just a few steps.
- Browse to the Geoprocessing content section of the ArcGIS Resource Center.
- Find the Model and Script Tool Gallery link on the left side of the page.
Here, you’ll also find the following helpful resources: Submission guidelines and Submission checklist. The submission guidelines page will provide tips for organizing your data. The submission checklist page will help make sure you haven’t left anything out, such as scrubbing your data, setting relative paths, or removing old results from the map document results window.
3. Compile the tools and data into a ZIP folder according to the submission documents.
4. From the Model and Script Tool Gallery page, click Add an Entry.
5. On Add Gallery page, enter the information about your submission, upload a zip file for the tool and
add a thumbnail graphic. Click the Submit button and you’re done.
By following these quick and easy steps, you’ll be on your way to sharing knowledge and experience with the ArcGIS community, helping others become more efficient in their workflows and processes.
-Timothy H., Support Analyst – Geodata Raster Group, Esri Support Services – Charlotte, NC
Let’s pretend you’ve been tasked to build a geoprocessing model to automate some of your department’s data management tasks while everyone is out of the office. Since ModelBuilder doesn’t have any magic buttons for scheduling times to run or people … Continue reading
Imagine you’re the GIS Data Manager for New York City and receive a request for data from a consultant for Central Park. The data request included roads, streams, soils, buildings and other feature classes that are stored in the master geodatabase for the city. Instead of providing the entire geodatabase, you clip the data down to just the park boundary. Continue reading