I am in the midst of installing a scanning mini micro pulse LIDAR, which would be purposed to measure the cloud height profile of the atmosphere.
The cloud height profile will be match with satellite images, and thus I would require both spatial coordinates, and the angular offset of the instrument from true north. For the former, I have a GPS to do it for me, but I have difficulties in determining the latter.
Inspired by a sun photometer, I thought it might be possible to use the known solar angle from a sun tracker, and a well aligned pinhole and light sensor.
I would attach the aligned pinhole and light sensor to the equipment, and maximize the light detector's reading by adjusting the equipment's angular position.
This however would require me to attach the aligned pinhole and light sensor to the scientific instrument.
Is there a better way to do this? Or does anyone have a recommendation for the calibration set-up I was talking about?
Use your cell phone for true north if you have service where you are doing your measurements. If you dont have cell service use your GPS twice. Once for the local of your measurement then move your GPS offset in line of where you are pointing. You can then calculate true north from the vector of your 2 GPS points.
In dealing with optics, I don’t think this is an accurate approach. Moreover the phone has to be inline with the scientific equipment, which is difficult to ensure with a phone
In pre-GPS days, surveyors measured the alignment to magnetic north with a compass and corrected to true north by adding the local magnetic declination, which could be read from a map or chart.
Magnetic compasses still work, and online calculators are available for current and historical magnetic declinations. Here's one from NOAA:
https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml
In Singapore, you'd need to adjust your magnetic angle by about 16 hundredths of a degree.
- Badges
- Science topic