Recently in Analysis Category

Go Matsumoto, a graduate student at Southern Illinois University at Carbondale posted his MA thesis on Academia.edu. The work is entitled, "Pachacamac GIS Project: A Practical Application of Geographic Information Systems and Remote Sensing Techniques in Andean Archaeology". This thesis is a wonderful case example that incorporates the use of archival maps and new data to produce an outstanding GIS of the site of Pachacamac, Luirn Valley, Peru. Click on the title above or click here to download or read this thesis.

Tutorial video showing how to use ArcMap 9.3 to calculate 1) nearest neighbor analysis on a distribution of points and 3) find the closest feature for that same distribution of points. Be prepared that this is my very first video tutorial. Is this useful? Let me know what you think...

 

Many areas of agriculture are impacted by salinization. This problem can be particularly acute in arid regions. ASTER provides a means by which soil salinity can be examined. Below is the ENVI band math used to calculate a soil salinity index image from ASTER imagery. The index is based on Al-Khaier's (2003) MS thesis and it is validated with field measurements of soil salinity.

The band math is as follows:
(float(b4)-float(b5)) / (float(b4) + float(b5))

The equation must be performed with the float parameter.

Craig is presently applying this transformation to examine the spatial pattern of salinity in relation to the distribution of q'ochas in the northern Lake Titicaca Basin.

REFERENCE
Al-Khaier, F.
    2003    Soil Salinity Detection Using Satellite Remote Sensing. Masters of Science, International Institute for Geo-Information Science and Earth Observation.

Another Interesting Reference:
14.00 Fernando Caceres, Hamid Ali-Ammar, Eric Pirard (Universite de
Liege, Belgium)  - Mineral mapping in salt lakes from Sud Lipez
(Bolivia) using ASTER images.

Some hints on looping
This post suggests that record by record looping is not possible. Specifically, it states "You can't pass a row object to a gp tool" The first thread gives python code for taking a directory of feature classes and calculating pathdistance from those. The second thread tries to calculate costdistances on several records in a single file. The conclusion is that the single file with multiple records needs to be converted into multiple files each with one record. I believe that the crime analysis tools has the capability of taking multiple records and making a theme from each record.

Reading to the bottom of the post it looks like there is a python solution which will loop through.

Some notes on pathdistance mapping related to the guide written by Nico

Nico's most recent notes can be found here.

Here is the command line for PathDistance:
PathDistance_sa Places C:\WorkSpace\PathDis_Plac2 # dem5792 # 'BINARY 1 45' dem5792 'TABLE C:\WorkSpace\ToblerAway.txt' # C:\WorkSpace\PathDis_Bk2

Here is the command line for CostPath
CostPath Qocha_Centroid PathDis_Plac3 PathDis_Bk3 C:\WorkSpace\CostPat_Qoch1 EACH_CELL ORIG_FID

Strategies for creating profile graphs in ArcMap

The links below lead to a couple of interesting tools for conducting viewshed analysis in ArcMap.

ViewShed for each DEM point / Weighed Distance

http://arcscripts.esri.com/details.asp?dbid=13500

This aml had to be run from workstation. Note: On first run, the aml failed. N Craig has contacted the author. Craig has a revised version.

Automate viewshed analysis

http://arcscripts.esri.com/details.asp?dbid=14687

Burn multipatch into DTM custom geoprocessing tool

http://arcscripts.esri.com/details.asp?dbid=15173
This allows for buildings and other objects to be burned into a dem so that surface analysis can be performed in urban spaces.

This post details notes on joining tables with ArcView3.x and using this software to make the joins permanent.

This post contains some notes on ArcMap Field Calculator expressions that are useful for analysis of polygons.

The following expressions can be used to calculate various parameters of polygons.

A_i as the Area of polygon i, and L_i as its perimeter length, and B_i as the area of a circle with perimeter L_i, then example measures include:

Perimeter/Area ratio (P1A):

Algebraic Formula:

ArcMap Field Calculator Expression: ([Shape_Length]/[Shape_Area])

Because the value of the index changes with the size of the figure, this ratio is unsatisfactory for most comparative applications.

Perimeter²/Area ratio (P2A):

Algebraic Formula: 

ArcMap Field Calculator Expression: ([Shape_Length]^2/[Shape_Area])

If preferred, this index, or its square root may be adjusted so that its value equals 1 when applied to a circle of the same area as A_i.

Shape Index or Compactness ratio (C):

Algebraic Formula:

_{ArcMap Field Calculator Expression:} Sqr([Shape_Area]/(([Shape_Length]^2)/12.56))

This ratio is dimensionless (it is unaffected by the size of the polygon) and it has a value of 1 for a circular region and a range of [0,1] for all plane shapes. Sometimes the index is computed as [1‑C_i].

Many useful functions are available at ESRI's ArcScripts. I also bookmark scripts that look especially useful for archaeology or anthropology. However, sometimes figuring out how to add this new script into ArcMap is so frustrating that it can feel like one is about to have their head chopped off...To help minimize these frustrations, this post details information on how to add user created scripts to ArcMap.

Scripts are written in a number of different languages. Each of these requires slightly different methods to connect the script to ArcMap. It can be confusing to figure out how the scripts need to be integrated into the program so that the scripts can be used. Descriptions are given for adding functions in the following formats:

• Arc Macro Language (AML)
• Avenue
• Visual Basic (VB, VBA, VBScript)
• Python
• Model Builder

Guide adapted from http://www.acadweb.wwu.edu/GIS/tut/ArcScripts.htm

The link below leads to Nico's notes on cost-distance mapping in ArcMap.This is a very very good place to go for information on how to run Tobler's hiking function using ArcMap.

http://mapaspects.org/courses/gis-and-anthropology/workshop-2009-viewshed-and-cost-distance/ii-cost-distance-2009

This post contains notes on calculating volumetric estimates from an excavation DEM.