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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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5.0

Nesting a hash within itself

Anonym

Lists and hashes have always been one of my favorite tools in IDL due to their versatile nature. A cool trick is that a hash can be stored recursively within itself. For example:

 

h = hash()
h['myself'] = h

 

With only level, this may not be particularly useful. However, this trick can be powerful for creating loops of information. Take days of the week, for instance. For fun, I'll use a DICTIONARY instead of a traditional hash, which has the convenience of the dot syntax for access.

 

Monday = dictionary('today', 'Monday')
Tuesday = dictionary('today', 'Tuesday')
Wednesday = dictionary('today', 'Wednesday')
Thursday = dictionary('today', 'Thursday')
Friday = dictionary('today', 'Friday')
Saturday = dictionary('today', 'Saturday')
Sunday = dictionary('today', 'Sunday')

 

Now define each day's tomorrow:

 

 

Monday.tomorrow = Tuesday
Tuesday.tomorrow = Wednesday
Wednesday.tomorrow = Thursday
Thursday.tomorrow = Friday
Friday.tomorrow = Saturday
Saturday.tomorrow = Sunday
Sunday.tomorrow = Monday

 

 

We can now loop through these days indefinitely. If we take Monday and request "tomorrow" seven times, we get Monday back again:

 

Next_Monday = Monday.tomorrow.tomorrow.tomorrow.tomorrow.tomorrow.tomorrow.tomorrow

 

We can store additional information in each of these hashes/dictionaries, such as a schedule for each day. 

 

Monday.Morning = 'Math 251, 9:00-10:00, Room 304'
Tuesday.Morning = 'Writing 301, 10:00-11:30, Room 211'

etc.

If today = Monday, then we can get today's morning schedule calling today.Morning. At the end of the day on Monday, we can say today = today.tomorrow, and tomorrow is the new today. Likewise, if we want today's morning schedule, we call today.Morning. 

Loops, routines, and cycles, are very common in the world as well as in scientific data. This method of information storage can be used for displaying radar data loops, with each frame stored in a hash that contains a "previous" and "next" frame. Additionally, it could be used for modeling states of pendulum or circular motion. It can be used for storing geographic information, such as time zones containing UTC offsets. There are probably many additional use cases.

As always, use caution with recursion. It is always unfortunate to find yourself killing code because it is stuck in an infinite loop. That said, be aware that JSON_SERIALIZE will not work in the examples above. Fortunately, given this use-case, there is no significant need to serialize the hashes' information into a string.

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