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David,

Years ago I used a digital caliper as a kamal / cross staff. A piece of exposed 35mm camera film taped to the upper served as a sun filter. A tiller extender was used as the baseline. Measurements to the tenth of a millimeter produced repeating intercepts to better than 4' on low altitude observations. Timing a sunset is generally the better way to go if the horizon is clear. 

Greg Rudzinski

From: David Pike
Date: 2017 Jan 15, 01:30 -0800

John you wrote:  Now consider a liner scale , aka a tape measure.

My first thoughts were to make 'just for fun' an improved ‘latitude stick’ using a digital Vernier calliper and tangent tables, finding one's natural arm’s length in the first instance by comparing the measured height of a planet with its calculated height.  However, I soon found it’s only repeatable at full arms length, so it would only work for the small heights you probably wouldn’t want to use for celestial in any case.  I decided to wait until the weather warms up before testing the idea further.  Living inland, the horizon would have to be an led at eye height on a gatepost.  DaveP