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Roppelcaver wrote:Sometimes, either the backsight or foresight may not be practical to shoot. In these cases, we double-shoot from one direction, making sure we reset our position between each of the compass and/or clinometer reading (helps catch a repeated error).
Sometimes, either the backsight or foresight may not be practical to shoot. In these cases, we double-shoot from one direction, making sure we reset our position between each of the compass and/or clinometer reading (helps catch a repeated error).
We augment this with a compass course to account for differences in how instruments read, and also to provide correction values (declination + variation) for true north and true horizontal. For us, a course is important: Suuntos vary by up to a couple degrees (inclinometers by perhaps a degree), and declination changes over time are substantial. And, the course also allows us to use more than one set of instruments with equally good result.
Roppelcaver wrote:Around Mammoth Cave, real declination versus USGS calculated has a substantial difference, and this also varies over time. In big caves, this is a significant variable (easpecially long, multi-year projects) and needs to be carefully considered.
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