Latest Contributions by JontyKnox

‎12-22-2011

Hi guys, Thanks for all the replies. So I finally figured it out, what I did was this: Bounding by Rectangle> Open attribute table of new .shp> Add field-"Bottom_Width"> Field Calculator- "Bottom Width= (2*Shape_Area/Shape length)-MBG_Width" 'MBG Width' is the maximum shape width at the top of the trapezoid defined by the bounding rectangle. While this does work, it is not as accurate as it could be, some of my trapezoids are slightly more irregular than I would like so it means there is between a 0.5-2.5ft margin of error. This was acceptable but it would be an interesting task to try and improve upon this in the future. Thanks again for all the help, it was much appreciated.

‎12-15-2011

Hi Chris, The tricky part as you identified is figuring out the skinny part of the trapezoid, and many of my polygons also don't have just the 4 coordinates... It's been giving me a real headache. I'm going to have a swing at the python you showed me though. See if it yields any results. I'll let you know how it goes. Cheers, Jonty

‎12-15-2011

Hi Dan, While the bounding tool did work on normal polygons, as you can see from the attached images, the irregularity of the ones I am dealing with, did not really work out: I tried convex hull, which did work, but did not provide the shortaxis etc that the bounding with rectangle did. Any ideas?

‎12-15-2011

Example of polygons I have to calculate width for:

‎12-15-2011

Hi there, I'm having a problem calculating polygon width. Essentially I have a number of polygons (1000+) that are all irregular, majority trapezoids but some others that probably don't even constitute a shape. What i want to do is find out the width of the polygons at their base (lets call this the shortest width of the trapezoid) and at their top (the largest width of the trapezoid). Any ideas on how I could go about this? Attached is a picture of what I'm dealing with here:

‎12-01-2011

Thanks for the quick reply. SORT is the table name and is not a reserved word in my DBMS. I just broke the query down to basics and the Boolean part works, as does the 'departures' section- only if I change it from Max to some other function such as >10 however. This leads me to think that perhaps the problem is with the MAX function? Cheers,

‎12-01-2011

Hi Bruce, So I constricted this from what you gave me, I've tweaked the database slightly since my last post, but the statement accurately reflects what I want to do: SELECT MAX( "Departures" ) FROM SORT AND "Boolean" =0 However, when I verify the statement it still gives me the 'Invalid SQL statement was used' (twice). Any advice what I've messed up with the syntax? Thanks, Jonty

‎11-29-2011

Hi there, I am trying to construct an SQL query using the 'Select' tool. Essentially what I am trying to figure out is how to select the first row in an attribute table, with an additional statement only allowing this record to be selected if my Boolean field (in the same attribute table) is equal to 0. For a bit of background, this step fits into a wider process that I am running in Model builder. The tool factors into a structure that would then create a buffer around the highest ranked points (FID moving from 0 down) in the attribute table. It would then exclude those points that fall within the buffered regions around the highest ranked points (by assigning them a value of 1). This process would repeat until all points had a Boolean field value of 1. If you guys could lend me a hand that would be great, Cheers, Jonty

‎11-29-2011

Hi Dan, Sorry for the late reply. The project got shelved for a bit while I was away. But what you recommended turned out brilliantly. Thanks for the help, as always I appreciate it. Cheers, Jonty

‎11-17-2011

Hi, So I'm having a slight problem with a point shapefile. Essentially the points represent a number of global ports. However the precision of these global ports is skewed i.e. some ports are inland when they should on the coast etc. What I want to do is snap these points to a continental line shapefile. Ordinarily I would use the 'Snap' (Editing) tool. However there are other ports that are supposed to be inland and snapping the whole point shapefile to the continental outline would make those points that are meant to be inland change to coastal. Essentially what I would like to do in this case is apply some form distance function i.e only snap those ports �?�40km from the coastline. Ideally I would like to use a pseudo snap pour point tool, but this only works with a flow accumulation grid but does have the distance function I was looking for... Any ideas about what I could possibly do?? It seems as though all of the functions are there in Arc but they just aren't present in one conclusive tool... Cheers, - Jonty

‎10-28-2011

Hey Dan, That made sense, thanks for the help. It worked out well in the end. Cheers, Jonty

‎10-21-2011

Hi there, So I have a DEM and a line .shp file. What I want to do is obtain the mean elevation for each line segment. Relatively simple, I just used the Zonal Statistics as table tool. However I run into a problem when I try and join these average elevation values back to the original line data. There are no spatial coordinates in the table so I can't so a spatial join and when I conduct a normal Join, the Zonal Statistics Table has not maintained the original FID values from the line .shp file. Any ideas on how I can solve this one? Thanks, - Jonty

‎10-12-2011

That worked fine for that element of the project but I have another similar step that I'm struggling with: Essentially I have two different Point .shp files and I need to find the nearest neighbors to one point shapefile using the other. For example, I have 7 species sightings at various locations and I need to identify the nearest ports to those species sightings. The nearest neighbor tools in Arc only allow for one .shp file input, not the two .shp files I require in this case. Thanks, Jonty

‎09-30-2011

Hi Ravi, You don't need a common field to join and relate to. A spatial join does it based upon spatial data inherently stored within the polygons and points. Right click on the layer, i.e. The point file>Joins and Relates> Join...>Select 'Join data from another layer based upon spatial location' from the drop down menu in the dialog box. The choose the layer to spatial join to, I'm guessing the polygons, then choose between 'Falls inside' or 'Closest to it' based upon your own preference. This will give you a new layer with the polygon attributes joined to the point data.

‎09-30-2011

Hi Ravi, it may just be easier for you to use the 'Spatial Join tool'. Its the same as Joins and Relates but instead assigns attribute values based upon spatial location. If you right click on the layer you want the attributes added to... I'm guessing the points, select join and relate and then go from there. Let me know how it works out for you, Cheers, Jonty

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My Ideas

Latest Contributions by JontyKnox

Re: Polygon Width

Re: Polygon Width

Re: Polygon Width

Re: Polygon Width

Re: Polygon Width

Re: SQL Select Query

Re: SQL Select Query

SQL Select Query

Re: Snapping points to line

Snapping points to line

Re: Joining Zonal Statististics to feature

Joining Zonal Statististics to feature

Re: Finding Closest Distance Between Points

Re: Extract Value to points

Re: Extract Value to points

Re: Polygon Width