Bruce Dawson
Active Member
Hello everyone,
I have a question regarding the compass heading as it shows in my system. I use the offset point routine quite often, typically for points that are nearby (3-10 feet away) like under a pine tree or for a building corner that I cannot get directly. I shot a powerline tower the other day that was perhaps a thousand feet away across a river, just needing it for line, not position. After reducing the data on top of an ortho photo that actually showed the powerlines, it was substantially off to the north. Reading through the manual, it indicates that the compass heading is based on the coordinate system, with "Global" systems showing the True North bearing, and "Local" showing the Grid bearing (in brackets). I use NAD83(2011)/Washington North/NAVD 88.
I am wondering then if my compass heading from the "Set by Compass" option in offset is actually True? For my close topo shots that is not an issue. I have the "B" option set to Grid in the offset screen, and actually the heading captured in the Set by Compass screen is in brackets. Why then is my point so far to the north?
I have attached an image showing what I have. The point shot by offset is the one in the river to the north of the powerlines, again, I shot it for line only from a position directly under a tower on the east side of the river. You can just see the powerlines in the ortho as light white lines.
I have a question regarding the compass heading as it shows in my system. I use the offset point routine quite often, typically for points that are nearby (3-10 feet away) like under a pine tree or for a building corner that I cannot get directly. I shot a powerline tower the other day that was perhaps a thousand feet away across a river, just needing it for line, not position. After reducing the data on top of an ortho photo that actually showed the powerlines, it was substantially off to the north. Reading through the manual, it indicates that the compass heading is based on the coordinate system, with "Global" systems showing the True North bearing, and "Local" showing the Grid bearing (in brackets). I use NAD83(2011)/Washington North/NAVD 88.
I am wondering then if my compass heading from the "Set by Compass" option in offset is actually True? For my close topo shots that is not an issue. I have the "B" option set to Grid in the offset screen, and actually the heading captured in the Set by Compass screen is in brackets. Why then is my point so far to the north?
I have attached an image showing what I have. The point shot by offset is the one in the river to the north of the powerlines, again, I shot it for line only from a position directly under a tower on the east side of the river. You can just see the powerlines in the ortho as light white lines.
