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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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Dynamic Plots Using an Equation String

Anonym

The PLOT function's new Equation argument adds flexibility to the creation of plots in IDL, allowing you to create dynamic, interactive output.

The Equation argument on the PLOT function allows you to specify either a string containing an equation with variable X, or the name of an IDL function that accepts X as an input argument. The result of the equation (or the function) should be a one-dimensional array of Y coordinates to be plotted.

  • If Equation is an expression, then the EXECUTE function is called once with the X array. Note that in certain circumstances (such as the IDL Virtual Machine), you may not be able to use the EXECUTE function.
  • If Equation is a function name, then CALL_FUNCTION is called once, with the X array as an input argument. The function should return a one-dimensional result array.

Once IDL creates the plot output, if you then interactively adjust the plot range, IDL will automatically recompute the equation to cover the new range.

We'll use the BESELJ function in IDL to show how to use a Function String in the Equation Argument:

 

; Plot J Bessel Functions

pj0 = PLOT('BESELJ(X, 0)', XRANGE=[0.0, 50],  $

  XTITLE='X', YTITLE='$J_n(x)$ or $Y_n(x)$', $

  TITLE='J Bessel Function')

pj1 = PLOT('BESELJ(X, 1)', 'r2', XRANGE=[0.0, 50], /OVERPLOT)

pj2 = PLOT('BESELJ(X, 2)', 'b2', XRANGE=[0.0, 50], /OVERPLOT)

; Annotate the plot.

xcoords = [1, 1.66, 3]

ycoords = [.8, .62,.52]

labels = '$\it' + ['J_0','J_1','J_2'] + '$'

  t = TEXT(xcoords, ycoords, labels, /DATA)

 

If you run the code above, it should generate a graphic like this:

Once IDL creates the plot, test out its dynamic capabilities:

  • Try clicking with the middle mouse button on the graphic and panning around.
  • You can also use the mouse wheel to zoom in or out, or hold down the <Shift> key and draw a zoom box.
  • Change the plot range programatically at the IDL command line:

pj0.xrange=[0.0, 150]

As you change the plot range, IDL recomputes the equation with new X values that span the new range.

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