Latest Contributions by DavidMedeiros

‎02-09-2017

Thanks Dan. I was hoping Timothy would have been able to get the info direct form the GP dev team. I'll pass your suggestion on to the researcher.

‎02-09-2017

Hi all, just checking in to see if there's a response from the GP team on this question? Thanks! David

‎01-24-2017

Thanks guys!

‎01-23-2017

Thanks. I'm not actually the researcher in question but am helping track this down for a PhD candidate who's a patron at my center. I don't think he's doing any comparative analysis between algorithms, rather he's compiling reference information for his works defense where he may very likely be asked, "which min spanning tree algorithm did you use?". The answer can't be "I don't know" or "the one Esri uses" ; ) Esri tools usually post the specific algorithm details on the help pages so I was surprised this wasn't there. Unless it really doesn't matter in practical terms which is used?

‎01-23-2017

I have a student who is using the Cost Connectivity tools in ArcGIS for his research who needs to know the specific algorithm being used in the tool to determine the minimum spanning tree. The ArcGIS online help only refers to the linked wikipedia article for more detail on the method, but there are several algorithms listed there. How can he determine the specific one being used in the arcGIS tool? How the Cost Connectivity tool works—Help | ArcGIS Desktop Minimum spanning tree - Wikipedia

‎09-03-2015

That seems like a hassle. Why wouldn't the Web App also auto generate a thumbnail or take it from the Web Map it was created from?

‎05-14-2015

I have a student who is doing an analysis of hydraulic head along water transmission pipes in LA. He has an elevation surface and the total lines connecting various facilities across LA county. What he needs from this data are to break up the transmission lines into segments based on uniform slope. So along the path of the transmission line we'd break the line up into smaller sections based on that section having a roughly constant rise/run. We don't need segments of even elevation. A slope surface wont help as we need the slope along the direction of pipe, not in the direction of the steepest terrain. We can't just calc rise over run for his segments becasue we don't have the run part. We are basically looking for the natural breaks in elevation changes and making segments between those breaks. This seems straightforward but has been very difficult to work out. Any ideas for a workflow? - david

‎05-13-2015

That's what I'm finding. Enabling Z values in the environment doesn't seem to effect the out put of a Data > Export Data flow that won't help quickly create a Z aware copy of the data. Maybe I can hunt down a tool that will use that environment setting. Like I described above, it's easy enough to re import points from a table and add the Z awareness then, but what would a user do who receives an existing 2d line for say trails in a park and then ants to use some of the 3d tools that require a Z aware line layer. Would they have extract the nodes, export an xy table, re import with Z values, the re connect the nodes into lines? Seems absurd.

‎05-13-2015

To help clarify the question. I'm not looking for ways to visualize or represent the data in 3d, but to make the properties of the data change from not having Z values to having Z values. If you check the properties of any GIS data layer you will see an indication of the presence or absence of Z values for that data. For point data for instance I know that you can make them Z aware while creating them from a table of XY coordinates. But for existent GIS data, is there a way to make them Z aware after the fact?

‎05-13-2015

Many (all?) 3d tools only work with Z aware feature layers. Is there a way to take an existing point, line, or polygon data layer that has no Z values and make it a Z aware layer without having to re import the points or digitize the the lines or polygons into a new layer?

‎02-19-2015

Step one of almost any research project here is to get out of GCS, unless the interpolation that causes changes the raster values we need to evaluate. With data like LandScan global pop rasters you don't want interpolate the pop values before measuring them, the same might be true of the night lights data but I think the variation is probably minimal at the admin 2 level. My stats background is limited so I wasn't aware that you could derive the percentile from the mean and standard deviation. I doubt the data are going to be normally distributed though, it's likely to be a skewed distribution for many parts of the world with far more dark pixels than very bright. I'll have the researcher sample a few zones to be sure. Apart from that I take it there is no simple method for tackling this question? Even breaking the raster up by admin 2 zones before vectorizing seems daunting.

‎02-18-2015

I'm helping a researcher who is evaluating the pixel statistics of Night Light data by admin zone. She wants to calculate (along with normal zonal stats) the 5th and 95th percentile values for pixels in the raster by zone. Given a raster with an attribute table, this would seem easy enough to accomplish but I can't figure out how to do this without tackling a conversion of the raster to points to allow for a spatial join between pixel values and admin ids before exporting to a table. Not practical for a global raster dataset. Any help is appreciated. David

‎12-17-2014

I have a 3d density surface representing water sample data taken along a stream network. I would like to visualize this as spikes just along the stream bed. Is there a way to take the surface I have and trim it to some linear feature (like a 10 or 20 meter river buffer), so the spikes remain but the edges are clipped or trimmed at the edge of the buffer? I tired extracting the surface by the buffer and setting the base height to the extraction and that results in a ribbon of pixels at the Z value higher but there is no fill to the bottom of the surface (like an extrusion).

‎12-11-2014

Thanks Mike, That looks to be relevant only to the Enterprise Login function, which I don't have set up at the moment. I inherited management of our account and need to investigate the Enterprise function at some point. That said, I would think this would be a general Roles function and available universally across AGO instead of just under Enterprise. David

‎12-10-2014

Thanks Heath, I thought I'd read or heard that AGO admins were able to set the default role to a custom role. I assumed this meant there was a AGO admin feature to change the default role as opposed to needing to script something. Too bad, seems like a simple and obvious add on to AGO control for Esri.

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My Ideas

Latest Contributions by DavidMedeiros

Re: which minimum spanning tree algorithm?

Re: which minimum spanning tree algorithm?

Re: which minimum spanning tree algorithm?

Re: which minimum spanning tree algorithm?

which minimum spanning tree algorithm?

Re: Thumbnails for Web Applications

Line segments from uniform slope along a path?

Re: How can I make an exisitng 2d polyline layer Z aware?

Re: How can I make an exisitng 2d polyline layer Z aware?

How can I make an exisitng 2d polyline layer Z aware?

Re: Raster value percentiles by zone?

Raster value percentiles by zone?

Trim 3d surface by line or poly features?

Re: Enterprise login and roles

Re: Enterprise login and roles

Re: Rectified 16 bit tif appears black in PhotoSho...

Collect GPS locations by angle and distance offset...

Can you copy symbology from one Feature Layer to a...

Add an Extent parameter to Disperse Markers tool

Re: Thumbnails for Web Applications