Ham Radio to Learn KML: Elevation maps

I started out wondering how to attach videos to kml maps and wound up working on elevation profiles. There's always something new to learn on this project. It's pretty cool!

There's something I've often wondered about with respect to QRP on twenty meters with low antennas: how much help is the rig getting from the slope of the hillsides I transmit from? Using Google Earth elevation profiles, It looks like I'll be able to get quantitative answers!

The Goal

Map the elevation profile of the terrain Project TouCans is situated on in the direction of the transmit path to the other station in a give QSO (radio contact.) The idea is to wind up with something like this.

The Steps to Get it Done (First Prototype)

Issue:

The elevation profile from station to station tends to be very long. I'd like to only look at the profile over a few twenty meter wavelenghts. I don't see any zoom controls in Google Earth for the elevation pofile, so I'll plot a shorter line on the map in the same direction, and then display the elevation profile for the shorter line. In the picture above, I've done this, the shorter line is a portion of the path from Albuquerque to Costa Rica.

Steps:

Calculate the distance from station to station using Datasette, specifically, the haversine plugin
From there, find the endpoint of a line segment starting at the transmitter and ending 200 meters away, (or however long you're interested in.)

Use the earthmid functions, earthmid.partial_path_lat, earthmid.partial_path_lng, passing in the total distance divided by the distance you're interested in (200 meters for example), as the last argument

And then you hit the kludge. Add a line segment, (linestring), from the tx station to the segment coordinates returned above to the QSO map you're interested in. View that segment in Google Earth Pro, right click the line and select 'Show Elevation Profile'.

Here are the results using a path from a US-0955 Petroglyph National Monument POTA outing I've been interested in for a while:

Rise over run data:

I was especially surprised to learn that Google Earth had even modeled the boulders on the side of the mesa:

Steps to Create the gif above from a screen capture using ffmpeg

ffmpeg -i elevgif.mp4 -ss 00:00:16 -t 00:00:29 -c:v copy -c:a copy elev_sh.mp4

ffmpeg -i elev_sh.mp4 -loop 0 -vf "fps=10, scale=640:-1" elev_sh.gif

References

From

https://ieeexplore.ieee.org/document/7152831

As more and more digital elevation data are available with better resolutions, it is getting more convenient to extract terrain features important for radio propagation modeling such as the mountain peaks and ridges. In [105], a simple method is used to extract 3D ridges from digital elevation data. The extracted ridges then serve as diffraction wedges in simulating the radio wave propagation. It is shown that 3D features of ridges, e.g., the orientation and elevation parameters, are necessary for accurate calculation of diffracted field. These 3D features are commonly ignored in widely used propagation modeling methods such as the knife edge diffraction. For multiple diffractions, the 3D features of ridges and their effect on the diffraction are investigated in [106].

and:

The Valentine's Day Magnetic Monopole

There's an assymetry to the form of the two Maxwell's equations shown in picture 1. While the divergence of the electric field is proportional to the electric charge density at a given point, the divergence of the magnetic field is equal to zero. This is typically explained in the following way. While we know that electrons, the fundamental electric charge carriers exist, evidence seems to indicate that magnetic monopoles, the particles that would carry magnetic 'charge', either don't exist, or, the energies required to create them are so high that they are exceedingly rare. That doesn't stop us from looking for them though! Keeping with the theme of Fairbank[1] and his academic progeny over the semester break, today's post is about the discovery of a magnetic monopole candidate event by one of the Fairbank's graduate students, Blas Cabrera[2]. Cabrera was utilizing a loop type of magnetic monopole detector. Its operation is in concept very sim

Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

Now available as a Kindle ebook for 99 cents ! Get a spiffy ebook, and fund more physics The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems , there seem to be fewer explanations of the procedure for deriving the conversion, so here goes! What do we actually want? To convert the Cartesian nabla to the nabla for another coordinate system, say… cylindrical coordinates. What we’ll need: 1. The Cartesian Nabla: 2. A set of equations relating the Cartesian coordinates to cylindrical coordinates: 3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system: How to do it: Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables. The chain

More Cowbell! Record Production using Google Forms and Charts

First, the what : This article shows how to embed a new Google Form into any web page. To demonstrate ths, a chart and form that allow blog readers to control the recording levels of each instrument in Blue Oyster Cult's "(Don't Fear) The Reaper" is used. HTML code from the Google version of the form included on this page is shown and the parts that need to be modified are highlighted. Next, the why : Google recently released an e-mail form feature that allows users of Google Documents to create an e-mail a form that automatically places each user's input into an associated spreadsheet. As it turns out, with a little bit of work, the forms that are created by Google Docs can be embedded into any web page. Now, The Goods: Click on the instrument you want turned up, click the submit button and then refresh the page. Through the magic of Google Forms as soon as you click on submit and refresh this web page, the data chart will update immediately. Turn up the:

Copasetic Flow

Search This Blog