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NV5 Geospatial Blog

Each month, NV5 Geospatial posts new blog content across a variety of categories. Browse our latest posts below to learn about important geospatial information or use the search bar to find a specific topic or author. Stay informed of the latest blog posts, events, and technologies by joining our email list!



Not All Supernovae Are Created Equal: Rethinking the Universe’s Measuring Tools

Not All Supernovae Are Created Equal: Rethinking the Universe’s Measuring Tools

6/3/2025

Rethinking the Reliability of Type 1a Supernovae   How do astronomers measure the universe? It all starts with distance. From gauging the size of a galaxy to calculating how fast the universe is expanding, measuring cosmic distances is essential to understanding everything in the sky. For nearby stars, astronomers use... Read More >

Using LLMs To Research Remote Sensing Software: Helpful, but Incomplete

Using LLMs To Research Remote Sensing Software: Helpful, but Incomplete

5/26/2025

Whether you’re new to remote sensing or a seasoned expert, there is no doubt that large language models (LLMs) like OpenAI’s ChatGPT or Google’s Gemini can be incredibly useful in many aspects of research. From exploring the electromagnetic spectrum to creating object detection models using the latest deep learning... Read More >

From Image to Insight: How GEOINT Automation Is Changing the Speed of Decision-Making

From Image to Insight: How GEOINT Automation Is Changing the Speed of Decision-Making

4/28/2025

When every second counts, the ability to process geospatial data rapidly and accurately isn’t just helpful, it’s critical. Geospatial Intelligence (GEOINT) has always played a pivotal role in defense, security, and disaster response. But in high-tempo operations, traditional workflows are no longer fast enough. Analysts are... Read More >

Thermal Infrared Echoes: Illuminating the Last Gasp of a Dying Star

Thermal Infrared Echoes: Illuminating the Last Gasp of a Dying Star

4/24/2025

This blog was written by Eli Dwek, Emeritus, NASA Goddard Space Flight Center, Greenbelt, MD and Research Fellow, Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA. It is the fifth blog in a series showcasing our IDL® Fellows program which supports passionate retired IDL users who may need support to continue their work... Read More >

A New Era of Hyperspectral Imaging with ENVI® and Wyvern’s Open Data Program

A New Era of Hyperspectral Imaging with ENVI® and Wyvern’s Open Data Program

2/25/2025

This blog was written in collaboration with Adam O’Connor from Wyvern.   As hyperspectral imaging (HSI) continues to grow in importance, access to high-quality satellite data is key to unlocking new insights in environmental monitoring, agriculture, forestry, mining, security, energy infrastructure management, and more.... Read More >

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Implicit Get/SetProperty calls in user-defined classes

Anonym

Operator overloading in user-defined classes was introduced in IDL 8 through the IDL_Object class. Mike Galloy explains how to use this technique here. One somewhat overlooked feature of IDL_Object is that it allows implicit calls to the GetProperty and SetProperty methods of a class. As a rule, member variables of an IDL class are protected, so you can’t access them directly outside the class definition. For example, COLOR is a property of IDLgrSurface in the Object Graphics (OG) system. Trying to access a surface’s color directly results in an error:

IDL> s = idlgrsurface()
IDL> print, s.color
% Object instance data is not visible outside class methods: S
% Execution halted at: $MAIN$

The correct way to get the surface’s color is through its GetProperty method:

IDL> s.getproperty, color=c
IDL> print, c
   0   0   0

Though this is by design, it’s (arguably) inconvenient. OG classes aren’t subclassed from IDL_Object, but it’s easy to create a new set of classes that inherit from both OG and IDL_Object. For example, here’s an extension of IDLgrSurface:

pro esggrsurface__define
   compile_opt idl2

   !null = {esggrsurface, inherits idlgrsurface, inherits idl_object}
end

This new class (ESG = Educational Services Group, a namespace I’ve adopted) is everything that IDLgrSurface is, but we also get the implicit Get/SetProperty feature of IDL_Object. Note that I haven't overridden IDLgrSurface's Init, Cleanup, GetProperty or SetProperty methods (though if I desired, I could, but that's a topic for another post). To see how this works, make a new instance of ESGgrSurface with some test data and get its color with an implicit GetProperty call:

IDL> s = esggrsurface(dist(30))
IDL> print, s.color
   0   0   0

Note that you must use the dot “.” method invocation operator to access this functionality; the arrow “->” operator won’t work here. Now change the color of the surface with an implicit SetProperty call and view it with XOBJVIEW:

IDL> s.color = !color.blue
IDL> xobjview, s

I’ve made extensions to a few of the OG classes (download them from here). You can use these as examples for subclassing other OG classes. I want to give credit to Jim Pendleton, one of my IDL gurus; I'm pretty sure I got this idea of extending OG from discussions with him. Read this subsequent post where I present a more detailed example of how this implicit Get/SetProperty feature works.

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