How Accurate is Your Distance Measuring Device? Visit the Santa Ana River Calibration Baseline to Find Out
I finally set time aside yesterday afternoon to go scout the area for my most accessible local Calibration Baseline. For a complete list of the official California Calibration Baselines visit this link: https://www.ngs.noaa.gov/CBLINES/BASELINES/ca
The latest published information for the Santa Ana River Baseline, as of July 9, 2020 is as follows:
There does not appear to be a dedicated parking area to access the site. The best and most friendly parking area I found within walking distance of the baseline monuments is at the U-Haul neighborhood dealer at 1967 N Main St, Orange, CA 92865. You can access a map here: https://www.google.com/maps/place/U-Haul+Neighborhood+Dealer/@33.8217542,-117.8748219,15.1z/data=!4m12!1m6!3m5!1s0x80dcd7485590f0d5:0x98c78df502c79364!2sTaft+Avenue+Community+Church!8m2!3d33.8154257!4d-117.8398888!3m4!1s0x80dcd70fc421613b:0xdde63280084194d0!8m2!3d33.8202568!4d-117.8674006
Park legally as close as you can and proceed westward towards a break in the chain link fence. The gate has been removed so access to the river bed is open 24 hours a day. However, the legal hours to enter vary between 7 AM and 6 or 9 PM, depending on the time of the year. During the Summer, long daylight hours, it is legal to visit the site until 9 PM. It is ideal to visit early or late in the day to avoid getting sun burnt.
I suggest making a trip to this site a community affair. Certainly, do not plan to visit and calibrate equipment on your own. It is too dangerous and inconvenient. I project the minimum ideal party crew will be six or more people. One or two at the origin of the baseline, and at least one each at the control points. Ideally, you will also place prisms with the same constants over each of the listed points.
When walking the area, I tried to look for secondary control points and monuments and found a few. It would be great to add more points to make angular measurement checks an easier affair. Most of the points lie on a straight line so horizontal angle measurements would yield tiny numbers. In retrospect, I wish I had brought a bike to move more rapidly between points. At a minimum, wear comfortable running shoes.
I have no idea where the Grid Factor = 0.983496 came from and I am curious how measurements taken at the baseline will differ with this setting versus a Grid Factor = 1.0
As I learn more about how to calibrate my trusty Sokkia Cygus KS-102PS total engineering surveying station, I plan to schedule visits to this Calibration Baseline. Please let me know in the comments if you have already visited this or another similar Calibration Baseline, and whether you would like to join me in one of my upcoming trips. It will be even more fun if you bring extra surveying stations and prisms.