Author: Dan

Geometry Operations with ArcMap Field Calculator

Field Calculator is one of the most frequently used tools within ArcMap: taught as part of nearly every introductory GIS course, it offers spreadsheet-like features to the normally static attribute table. Starting in ArcGIS 10.0, the attribute table also exposes the raw Geometry object of each feature to Field Calculator. This underutilized feature allows for rapid access to data that normally requires running a separate geoprocessing tool and joining the result to the attribute table. Building on my previous post about geodesic areas, I’ve compiled some of the more useful one-line geometry field calculations.

The doozy of an expression that inspired this cheat sheet.
The doozy of an expression that inspired me to post this cheat sheet.

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Seven-Week GRE Study Plan

After successfully completing the GRE last year, I posted my seven-week GRE study plan on the /r/GREhelp subreddit. Since that post is now locked, I’ve reproduced it here, along with a few other tips sent in direct messages.

I started studying about seven weeks before my test date, and studied in two phases. In the first phase (weeks 1-4), I mostly followed the Magoosh 1-month study plan and completed all of the associated lesson videos and practice problems, as well as 13/20 vocab flashcards decks. In the second phase (weeks 5-7), I did ETS/Manhattan/Magoosh practice problems, reviewed vocab flash cards, and took five practice tests. You can follow along with in the studying tracking spreadsheet; just Make a Copy to edit, and then enter your test date in cell D52.

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Unintentionally profound EPA: “All cohorts are subject to mortality”

Buried deep within the technical documentation of an EPA land use model is a profound philosophical insight. It’s not merely about the environment or land use, but about life itself:

Similarly, mortality is estimated by multiplying the number of people in given cohort times the cohort-specific mortality rates. The resulting number of deaths is then subtracted from the cohort. Unlike fertility, all cohorts are subject to mortality. Therefore, mortality rates are applied to each cohort.

Alright, I suppose it may be unintentionally profound.

This quote is taken from the documentation of the Integrated Climate and Land-Use Scenarios (ICLUS) model developed by the US EPA (12 MB PDF) . Unlike the US Census Bureau’s population projects, which only have nationwide tallies, ICLUS generates detailed population density and impervious surface rasters for the contiguous USA through the year 2100. This particular section of the documentation describes how the model accounts for births (fertility) and deaths (mortality) within the population during each time step.

This adage about the impermanence of life reminds me of the similarly unintentionally profound Wii notification: “Warning: Everything saved will be lost” as discussed on Reddit in 2013.

How the human mind finds meaning in the strangest places…