Added function json2satrec in io.js
#122
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Initialise `sgp4init` object and build `satrec` object from OMM data in JSON format. Ref: https://celestrak.org/NORAD/documentation/gp-data-formats.php
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Thanks for taking the time to help future proof this library! We need to add some unit tests for this new function. Might be smart to have at least a few that make sure it is getting the same answer as the original function. I'll take a look in the airport tomorrow, but the comment block on this looks incorrect. It mentions more input functions than are available. Additionally there are a lot of leftover comments from copying the original function - if we are modernizing the library there is no benefit of keeping old comments that don't apply. |
src/io.js
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| * | ||
| * Provide the OMM JSON format data as `jsonobj`, | ||
| * and select which standard set of gravitational constants you want | ||
| * by providing `gravity_constants`: |
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Unclear if you can actually provide gravity constants or if this old comments too.
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In this ported code, I cannot see the use of the gravity constants in any of the scorce code methods. Maybe this can be a new issue to be implemented.
| @@ -6,7 +6,7 @@ import sgp4init from './propagation/sgp4init'; | |||
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| /* ----------------------------------------------------------------------------- | |||
| * | |||
| * function twoline2rv | |||
| * function twoline2satrec | |||
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Can you explain why you are updating the name? Did you update the comments above too?
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Because classically, rv stands for satellite state vector: [rx, ry, rz, vx, vy, vz]. This represents the position and velocity in the x,y and z directions. But this function actually returns a satrec object.
This is not the same as a satellite state vector. A satrec object is a dictionary containing all the sgp4 satellite information [sgp4io.cpp].
I have not modified any other comments above. I figured that the old way on naming the function was not in-line with its modern interpretation of the term rv and satrec.
I did perform some basic tests, but I am not so proficient in JS, to write unit tests. But there seems to be a way to compare two objects using a method named The old and the new methods seemed to vary in the 8th decimal place due to some floating point magic which was beyond my understanding as a non-CS background person. this translates to a difference in a couple of milliseconds. If there are ways to check if these are within a certain tolerance while writing the tests, that would be optimal. |
src/io.js
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| * vallado, crawford, hujsak, kelso 2006 | ||
| --------------------------------------------------------------------------- */ | ||
| function json2satrec(jsonobj, opsmode='i') { | ||
| const opsmode = 'i'; |
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opsmode is passed as a parameter and defaulted to 'i'. This line of code would create a separate variable and cause the input parameter to be ignored. Please delete this line.
src/io.js
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| satrec.satnum = jsonobj.NORAD_CAT_ID.toString(); | ||
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| var epoch = new Date(jsonobj.EPOCH + 'Z'); |
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The use of var should be replaced with const.
io.js now has two exports and the import statements in a few files needed to be updated
Fixed a bug, reduced the number of lines of code, and converted one calculation into a constant for performance
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I opened a PR (spacenewb#1) on your PR to incorporate the changes I suggested and add the testing. |
Improvements to json2satrec
Implemented function `sunPos`, to calculate sun position. This resolves issue shashwatak#68 . The name of the function is slightly changed for clarity and added references. Cleaned the ported code `sun.js.txt` as provided in the original issue. Removed `var` declarations within the function to augment performance.
Added function
json2satrecinio.jsto initialisesgp4initobject and buildsatrecobject from OMM data in JSON format. Ref: A New Way to Obtain GP Data (aka TLEs).This is the new way of distributing TLEs and would become the new standard soon. It is better to port our functions slowly for compatibility.
#105