Tag Archives: Geoprocessing
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.
In order to clip the data, you have the options to clip the features individually or set up a batch clip. However, there’s a more efficient way. With the iterator functionality available in ArcGIS 10, a simple model using the Iterate Feature Class iterator and the Clip tool can provide an efficient way to extract the subset of data.
Within ModelBuilder add the Iterate Feature iterator (Insert Menu > Iterators > Feature Classes) and the Clip tool. Connect the iterator output feature class as the input to the Clip tool.
Below are the parameters that can be specified for each of the components.
- Iterate Feature Classes
- Workspace or Feature Dataset
- Feature Type
- Input Features
- Clip Features
- Output Feature Class
- XY Tolerance
For the clip output feature class, you can use a variable based upon the name being generated from the iterator. An example of this can be seen in the interface below with the percent symbols.
Based upon the variable for the output feature class name, the output of the model keeps the original name with ‘_clip’ added on.
After setting up the model and defining the desired parameters, this process can be accessed from your toolbox to easily clip a workspace or feature dataset for any project requiring you to work with only a subset of you master data.
The above model example can be downloaded from the ArcGIS Geoprocessing Model and Script Tool Gallery: Clip Workspace.
Timothy H., Support Analyst – Geodata Raster Group, Esri Support Services – Charlotte, NC
One of the things you may have noticed after upgrading to ArcGIS 10 is that the Spatial Analyst toolbar looks a little different. Sure, the Contour and Histogram tools are still there, but you may be asking, “Where are the other tools that were under the Spatial Analyst menu?”
ArcGIS 10 Spatial Analyst Toolbar
ArcGIS 9.3.1 Spatial Analyst Toolbar
The tools can now be directly accessed through ArcToolbox instead of the toolbar. This change makes the tools easily accessed through the Python environment. It also enables the environment settings to be set from a single location, whereas Spatial Analyst at 9.3.1 had its own environment settings. With everything in one location, the Spatial Analyst Tools can access the additional geoprocessing benefits.
You can also customize the Spatial Analyst toolbar to create a menu similar to that of the previous version. See Adding and removing tools on menus and toolbars for more information on customizing toolbars.
Remember, the toolbar will remain grayed out until raster data is added to the map, since it’s not functional with vector data. The Spatial Analyst Tools are still accessible from ArcToolbox when the toolbar is grayed out, though, as long as the extension has been activated.
Check out the related links below for additional information on the Spatial Analyst toolbar.
-Timothy H., Support Analyst – Geodata Raster Group, Esri Support Services – Charlotte, NC
Hello, this is Cassandra again, bringing you a blog post about my favorite thing about ArcGIS Desktop 10 – the Catalog window. In a nutshell, the Catalog window provides a tree view of file folders and geodatabases, just like in ArcCatalog, but directly within ArcMap. Need to add to add a feature class, but can’t quite remember where it is? Browse for it with ease in the Catalog window. Need to perform some geoprocessing and geodatabase organization but don’t want to shut down out of ArcMap? Do it in the Catalog window. Getting frustrated with schema locks on your geodatabases? Just stay in ArcMap and do your processes in the Catalog window.
The most common question concerning the Catalog window I’ve seen is ‘Where’s the preview tab?’. This question is easily understandable, especially since the Catalog button on the ArcMap Standard toolbar now opens the Catalog window, not ArcCatalog.
There is neither a Preview nor metadata tab directly available in the Catalog window. However, you can preview the data, view the metadata and more by right-clicking on the item and then select Item Description. The Item Description dialog box gives you access to view, print, edit, validate, export and import the metadata on the Description tab, as well as previewing the geography and table of the item on the Preview tab.
The Catalog Window includes a choice of three views as well. You can cycle through them by clicking the ‘Show Next View’ button.
For more information on the Catalog window, see the following help topic: What is the Catalog window?
Please leave any comments or questions that you may have under the Comments section below. NOTE: You must be logged in to your Esri Global Account to leave comments.
- Cassandra L., Desktop Support Analyst, Esri Support Services
Hey Everybody! This is Darrin from the Desktop group in our Eastern Support Unit. I just wanted to highlight some handy new functionality in the next release of ArcGIS.
If you’ve created custom toolbars in previous versions of ArcMap or ArcCatalog, you already know how convenient it can be to have a specific toolbar that contains only your frequently used or favorite ArcMap or ArcCatalog tools (instructions here). The process in ArcGIS 10 is basically the same, but you can now add your favorite geoprocessing tools to your new toolbar!
As long as you know the name of the tool or toolbox that contains the tool, you can easily drag and drop to your new toolbar:
- Click Customize > Customize Mode.
- In the Customize window, click the Commands tab.
- In the “Categories:” panel, select the toolbox that contains the tool you want to add. All toolboxes have ” Tools” appended to their names. For example, the Analysis toolbox will say “Analysis Tools”.
- Drag and drop the tool onto the toolbar as illustrated below.
- Close the Customize window and enjoy!
Having your frequently used tools in a custom toolbar can eliminate confusion, save searching time, and ultimately increase productivity when performing geoprocessing and other tasks in ArcGIS.
-Darrin C., Support Analyst – Desktop Group, Esri Support Services – Charlotte, NC