Bolschwilley Estate’s Lesson in Declination

The Bolschwilley Estate is a set of tracts located in San Patricio County, Texas out of the De Hibernia Grant. Conrad Blucher surveyed these tracts back in April 1940 when the owner was considering subdividing their land. Right away we can see that those subdivisions did not pan through, and instead only a couple of larger subdivisions were made. Ed Saulter, our lead georectification tech, was served a quick refresher on magnetic declination as he researched how the due north-south and due east-west highways could have tilted so much. Thanks to NOAAs Historical Magnetic Declination viewer, he was able to quickly verify that the 6 degree tilt was not an error made during the survey. For those that are unaware, magnetic declination is “the direction of magnetic north as determined by the positive pole of a freely suspended magnetic needle which is not subject to transient artificial disturbance.” (Ken Gold, Decisions) These shifts in magnetic declination occur naturally over time and play a vital role in boundary retracement.

That’s all this week from S{Q}L, Happy Thanksgiving everyone, may the blessings and turkey never come to an end!