Latest Contributions by JoshuaBrengel

‎02-18-2019

Thank you Dan, this is helpful. I believe the PRISM dataset is, generally speaking, based on station data that's been interpolated. Your zonal stat suggestions are appreciated. It certainly feels a bit overwhelming when considering all the variables that can change in not only projecting a raster, but also then further analyzing it via zonal statistics. So it's good to know that shooting for "less wrong" is an appropriate way to think.

‎02-18-2019

Thank you very much for the quick reply Dan. The original raster's cell size in DD is 0.04166667 x 0.041666667. Projected raster (to Equal Albers) is 4676.765775. Just using the 1 degree = 111,139 m w/out modifier, that is pretty close to each other. I'm assuming the concept of a modifier becomes important when I use the "Measure Tool" to get a geodesic line measurement. That's why even if the cell size says 0.0416 DD x 0.0416 DD in properties of original unprojected raster, when I measure the cell size of cell located in Florida in original raster it is measuring wider than a cell located in NY. Are there any other best practices I should consider when using the Project Raster tool? For example, should I set a snap raster or set my extent to the original raster in envt setting? I'm already assuming pick proper resampling technique for type of data (continuous vs discrete). Finally, any suggestions on resources for practical considerations for projecting rasters so that I have baseline expectations for should happen to my raster data upon projection? I realize this a few questions, though I think others could really benefit from your considerations! Thanks!

‎02-18-2019

I'm trying to project a PRISM precipitation raster to match a vector data's projected coordinate system so that I can perform zonal statistics on it. The original raster data has a GCS of NAD 1983 and I'm trying to project it into Albers Equal Area Conic. What should be the anticipated effect of using the Project Raster GP tool (ArcMap 10.4, SP1) on my original raster dataset? It appears that the cell size, extent, and spatial location have all changed between my original dataset and my projected dataset. I used measure tool to check cell size. Also, the suggested resampling technique for continuous precipitation data should either be cubic of bilinear, but regardless of what resampling I choose, there are changes to the original dataset. I'm not sure if these changes are to be expected and acceptable. From my couple days of research and discussions with coworkers, there are not a lot of available resources on the topic of raster projection and its best practices. Should I just scrap the idea of projecting the raster and use the dataset's original GCS for my zonal statistic analysis?

‎12-05-2018

Recently, I was told the following picture, which shows TWI (yellow cells) on a mixed forest/terraced agricultural landscape- was generated from a DEM that likely exhibits contour bias: Can someone please explain to me what contour bias is and how it happens in a DEM created from base LiDAR data? I assume it somehow refers to the overemphasis of contours that may naturally exists in LiDAR elevation data or even worse, the creation of artificial contours in the DEM? Is this caused by the interpolation and LiDAR processing methods when the DEM was created? This is of significant concern to me, as we hope to share the TWI with a large number of users. Thank you!

‎10-30-2018

Hi Emily, My apologies for just responding. Just saw your response. Unfortunately, I no longer have access to this data (was a contractor), so I'm trying to pull things from memory. I believe I was able to get a satisfactory solution. If I'm remembering correctly, I was able to get lines that were changed boundaries through time using a topology (upon conversion from original polygons to lines) and then further isolate changed boundaries using buffered current boundary lines. The issue was that sometimes there were gaps (ie broken boundary) between the changed (ie historic) boundary and the current boundary. I believe I used the Near tool to find the nearest XY coordinate on the boundary of interest. Then, I created a line to that point. Oh and be sure to use check and repair geometry tools to ensure single features, etc. Not perfect, but at least closed boundary gaps. I don't think I ever was able to find a way to convert back to polygons. Without knowing the specifics of your project, it's hard to provide great advice. Also, some of the tools- like Near- require an Advanced License for access. Wish I could be a greater help, though my memory has faded on this project. Best, - Josh

‎10-23-2018

Wondering the same thing when trying to create tile package from 1m x 1m resolution land cover dataset. I run through tile cache and package tools and end result is just a blank map. Have you found an answer? Are their certain resolution limitations when creating a tile cache/package?

‎10-15-2018

My ultimate goal is to do a step by step exact replication of a topographic wetness index workflow we've developed, but using a more recent LiDAR dataset (point cloud). I'm using ArcMap 10.4, windows 7 Pro and only have access to Spatial and 3D Analyst extensions. I have a couple questions about my approach: 1) The base dataset was downloaded in bulk from NOAA in .laz format. I used lastools' "laszip.exe" to convert laz files to las files. These .las files don't show up in ArcMap when browsing in Catalog or when using Add Data option. From my research online, it seems ArcMap can't inherently load laz format, but why can't I see the las files? Note: - I'm able to load las files into LiDAR tool (LAS to Multipoint) without tool giving me an error. 2) Our workflow first generates DEM by converting the las points to a multipoint shapefile and then using IDW. Yet, I've encountered numerous errors (i.e. Error 010067- Error in executing grid expression) when running LAS to Multipoint tool. Or, after successfully generating the multipoint shapefile, the points in the shapefile don't have associated elevation data which results in IDW error. The base LiDAR data comes in tiles and there are many tiles of LiDAR point data covering the area of interest for TWI analysis- in this case, an entire county. There are over 9 billion points in total. What's the best approach to break up the dense LiDAR dataset and still exactly replicate our workflow (must minimize impact on DEM generation to be run in further steps)? Note: - In LAS to Multipoint, I'm only using classes associated with ground and water points. - I've tried lasmerge to merge all lidar points into single file but that tool has 4 billion point limit. My research online suggests avoiding such a workflow anyways. My apologies if this seems like a loaded question. Trying my best to condense my explanation. Thank you for your suggestions! - Josh

‎08-13-2018

I should also add that ArcGIS Pro has a method for its Layout object called exportToPDF. It includes a "clip_to_elements" parameter, which appears to accomplish the same outcome as clipping to graphic's extent- albeit in PDF format. Could convert to a JPEG though. Perhaps Esri will add this new parameter as an option in the old "mapping" class module in future updates. Note: we haven't updated to ArcGIS Pro yet, so I'm not able to provide an actual test of this method for various layout types/formats.

‎08-10-2018

Hi Allison, Thought I'd follow up on this question. I was able to create a bit of a workaround that worked for me. You can convert your mxd to a pdf using "ExportToPDF" and then use "PDFToTIFF_conversion" to convert the pdf to an image: import arcpy import numpy as np import os basepath = r'L:\Projects\WIP_Toolbox' num = 1583 #Map Number i = 0 cntylist = ['County1']#County2, County3, County4, County5, County6, County7, County8] for cnty in cntylist: cntypath = os.path.join(basepath, cnty) inpath = r'L:\Projects\WIP_Toolbox\County\County_Wshds.mxd' # Input path for Watershed basemap outpath = r'L:\Projects\WIP_Toolbox\Test' outpdf = os.path.join(outpath, 'Test.pdf') outtiff = os.path.join(outpath, 'testimage.tif') mxd = arcpy.mapping.MapDocument(inpath) arcpy.mapping.ExportToPDF(mxd, outpdf, "PAGE_LAYOUT") arcpy.PDFToTIFF_conversion(outpdf, outtiff, clip_option = True, resolution = 250, color_mode = "RGB_TRUE_COLOR", tiff_compression = "JPEG") ‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ I'm self aware enough to realize this is not the most elegant/efficient solution and it may not work for other cases (ie for those whose purposes are better suited to a direct jpeg output or people who may have trouble clipping their picture in a more custom manner). But, for those comfortable exclusively with arcpy tools, it does remain entirely inside that domain. You can use the "RasterToOtherFormat_conversion" tool to get a JPEG (or another desired format)- though again, admittedly inefficient. At the very least, I'm hoping this answer spurs someone with more advanced skills in Python image analysis to suggest a more elegant solution using perhaps the Python package PIL or pillow. Hopefully, it provides a good first step though! - Josh

‎07-20-2018

Thanks for your help Michael! That's what I was hoping. I modified my scripts to import arcview prior to import arcpy.

‎07-20-2018

Use of licenses when python scripting. I only want to use arcview license unless tools in my script absolutely require use of arcinfo license

‎07-20-2018

Thanks for the quick reply Michael. I'm running ArcMap 10.4 Python 2.7 in IDLE. Based on my interpretation of the post you linked in your response above, it seems like there is conflicting information on if you can import arcview and not pull down the highest license level- in my case an arcinfo license. Xander seemed to claim he did not successfully import arcview but Ronald said it was possible to import arcview without pulling the highest level (to which Xander replied seeming to agree that conclusion). All that aside, I'm guessing I won't have an issue in 10.4 as long as I import arcview before I import arcpy? Also, it will only pull one basic licenses, not two basic licenses, if I run a script and then open up an instance of ArcMap, correct? Thanks again!

‎07-20-2018

I realize this is quite and old question, but rather than create a new post for the very same question: @ Clint Dow, did Curtis or Luke's suggestions work for you? I have the same issue. When running my python scripts where I import the arcpy module, I'd rather use the arcview license than the arcinfo license in order to keep the advanced license free for our GIS developer. Thanks!

‎07-17-2018

Yeah, I realize that was a limitation. See my recent reply. It may not be a best practice, but I based on the maps I'm creating, I won't need more than 7 text elements in the new map. So, I just created 7 text elements in the original map.

‎07-17-2018

Randy, Giving the text element a name worked like a charm in order to update the corresponding text, thanks! I still don't exactly know how I would copy a single text element from the original map, but I just created a bunch of text elements in the original map to pull from and rename in my new map. - Josh

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My Ideas

Latest Contributions by JoshuaBrengel

Re: Project Rasters- What are the best practices for continuous data?

Re: Project Rasters- What are the best practices for continuous data?

Project Rasters- What are the best practices for continuous data?

What is contour bias in a DEM?

Re: Removing slivers between polygon boundaries

Re: Tile Package Resolution/Scale limit?

Topgraphic Wetness Index using updated LiDAR

Re: Automating Clip Output to Graphics Extent with arcpy

Re: Automating Clip Output to Graphics Extent with arcpy

Re: 'Floating licenses' being taken by script

Re: 'Floating licenses' being taken by script

Re: 'Floating licenses' being taken by script

Re: 'Floating licenses' being taken by script

Re: Can't update TextElement text

Re: Can't update TextElement text

Re: Tile Package Resolution/Scale limit?

Re: Pythonw.exe Error

Re: Automating Clip Output to Graphics Extent with...

Re: Selecting Polygons Overlayed by Polylines

Re: arcpy.Point()- break down array/list/tuple to ...