Rank: 91 based on 714 downloads (last 30 days) and 23 files submitted
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Darin Koblick

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Company/University
California State University and Claremont Graduate University
Lat/Long
33.8078, -118.3698

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Professional Interests:
Astrodynamics

 

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Files Posted by Darin View all
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(last 30 days)
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30 Jun 2014 Screenshot Vectorized Multi-Dimensional Matrix Multiplication Take Any N-D Matrix and Multiply it by another N-D Matrix Without a For-Loop Author: Darin Koblick matrix, matricies, multiplication, vectorized, multidimensional, nd mtimes 58 0
06 May 2014 Screenshot Parallel Implementation of the Picard Iteration For Linear BVP PDEs Parallel Picard Iteration for a Linear Hyperbolic BVP PDE Author: Darin Koblick pde, hypberbolicsecond ord..., hyperbolic pde, parallel picard itera... 15 0
23 Apr 2014 Efficient Vector Rotation Matrix Routine Efficient Method to Determine a Matrix Needed to Rotate One Vector to Another Author: Darin Koblick vector, rotation, euler, angles, matrix, rotation matrix 33 3
12 Dec 2013 Screenshot Convert Keplerian Orbital Elements to a State Vector Convert orbital elements to a state vector, or a state vector back to orbital elements. Author: Darin Koblick keplerian, orbital elements, aerospace, conversion, position, velocity 49 1
  • 5.0
5.0 | 1 rating
18 Apr 2013 Screenshot Vectorized Solar Azimuth and Elevation Estimation Predict the topocentric solar position defined by geodetic lat, lon, Alt, and a universal time Author: Darin Koblick aerospace, alt, altitude, astronomy, az, azimuth 43 3
  • 4.0
4.0 | 3 ratings
Comments and Ratings by Darin View all
Updated File Comments Rating
23 Apr 2014 Efficient Vector Rotation Matrix Routine Efficient Method to Determine a Matrix Needed to Rotate One Vector to Another Author: Darin Koblick

Alexander, you are correct. I went ahead and changed the vector angle check to be closer to 1 instead of 0.99. Also, I found that I needed to add the case where vectors where close to parallel (i.e. abs(c) > 1-1e-13) and two or more components had the same values. Thank you for pointing out the problem to me.

01 Sep 2013 Convert ECI to ECEF Coordinates Transform ECI position, velocity and acceleration to ECEF position, velocity & acceleration. Author: Darin Koblick

Chad,

The two code lines you are referencing are trying to find the midnight that occurs before the provided Julian Date.

As written, the first check will be true if the Julian date occurs after midnight and 12+ hours before the time.

As written, the second check will be true if the Julian date occurs after midnight and less than 12 hours before the time.

If both checks are true, the code will use the last midnight that occurred. This is the desired functionality.

Because I am rounding down on the Julian date and subtracting a half day, there is no possible way that jd could be less than jdMin.

-Darin

20 Oct 2012 Convert UTC to Solar Apparent Time Convert a time given in UTC to Solar Apparent or Solar Mean Time Author: Darin Koblick

Brandon,

Also, if you are trying to compare the Solar Apparent Time, (SAT) be sure to input the longitude in degrees (W < 0, E > 0).

You can see that this function will match the solutions (almost exactly ... depending on the year) to those solutions in Example 4 of the ASTRONOMICAL INFORMATION SHEET No. 58 http://astro.ukho.gov.uk/nao/services/ais58.pdf

20 Oct 2012 Convert UTC to Solar Apparent Time Convert a time given in UTC to Solar Apparent or Solar Mean Time Author: Darin Koblick

Brandon,

Latitude and Longitude are needed to determine the input time value to the equation of time (UT). They aren't needed to determine the equation of time ... it has nothing to do with latitude and longitude. Perhaps you should compare to a location with a 0hr local time offset.

See this document for a description of what the equation of time is, you can also compare results to this as an "example". I don't guarantee any specific accuracy with EoT as it depends on the mean anomaly of the sun which is obviously a first/second order approximation.

http://www.ips.gov.au/Educational/2/1/14

11 Aug 2012 Convert ECEF to ECI Coordinates Take any vector or series of vectors in the ECEF Coordinate frame and convert them to ECI. Author: Darin Koblick

John,

35 leap seconds since 1972 sounds like that is indeed what you are seeing in STK. As you know, ECEFtoECI.m takes in a Julian date, so the correction would not be internal to this particular conversion routine.

In fact, I don't think Mathworks attempts to address this issue with their juliandate.m routine. You would more than likely want to make the leap second correction when converting UTC to Julian date.

Are you able to check for the estimated position differences using Julian date in STK instead of UTC? Perhaps this should make the comparisons a little more accurate as well.

Truthfully, unless you are trying to use this routine in high-precision satellite mission operations, as long as you are consistent with your coordinate frame conversions (i.e. always using these conversion routines), it really shouldn't matter if there are minor discrepancies with STK (it is all relative motion anyway).

-Darin

Comments and Ratings on Darin's Files View all
Updated File Comment by Comments Rating
08 May 2014 Lunar Azimuth and Altitude Estimation Algorithm Predict the Lunar Azimuth and Altitude within +/- .2 deg of any lat and lon for a given UTC Author: Darin Koblick Leo

23 Apr 2014 Efficient Vector Rotation Matrix Routine Efficient Method to Determine a Matrix Needed to Rotate One Vector to Another Author: Darin Koblick Koblick, Darin

Alexander, you are correct. I went ahead and changed the vector angle check to be closer to 1 instead of 0.99. Also, I found that I needed to add the case where vectors where close to parallel (i.e. abs(c) > 1-1e-13) and two or more components had the same values. Thank you for pointing out the problem to me.

22 Apr 2014 Efficient Vector Rotation Matrix Routine Efficient Method to Determine a Matrix Needed to Rotate One Vector to Another Author: Darin Koblick Alexander

Thank you for submission. But if cosine of angle between vectors is >.99 (by module), calculation is incorrect.
A pair f=[1 0 0], t=[0.9904 0 -0.1380] can be used as an example.

05 Dec 2013 Vectorized Clohessy-Wiltshire Hill Linear Propagation A Demonstration of Linear Satellite Orbit Propagation Using Clohessy-Wiltshire Equations of Motion. Author: Darin Koblick Son, juyoung

01 Sep 2013 Convert ECI to ECEF Coordinates Transform ECI position, velocity and acceleration to ECEF position, velocity & acceleration. Author: Darin Koblick Koblick, Darin

Chad,

The two code lines you are referencing are trying to find the midnight that occurs before the provided Julian Date.

As written, the first check will be true if the Julian date occurs after midnight and 12+ hours before the time.

As written, the second check will be true if the Julian date occurs after midnight and less than 12 hours before the time.

If both checks are true, the code will use the last midnight that occurred. This is the desired functionality.

Because I am rounding down on the Julian date and subtracting a half day, there is no possible way that jd could be less than jdMin.

-Darin

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