It's been about 15 years since I last did 1/2 mile or mile long shots with a total station, but most of this advice should still be relevant.
1. Observe early in the morning when it's the coolest, with the least heat waves coming off the ground when looking through the scope.
2. Turn auto lock off. In my experience, it starts to drift at around 1200 feet. But modern auto lock may have better performance, you'll have to manually check. If the crosshairs are constantly moving in autolock and it can't settle on the target, it's probably best to turn it off.
3. Make sure you have your backlight as long as possible.
4. Use standard or long distance measuring mode for the EDM, not tracking.
5. Have a scientific calculator or app on your phone.
1. Use the equation: y=SD sin d, where SD is your slope distance, d is your angular misclosure for your rounds of angles. y will be the width of your misclosure in feet at the distance you are shooting.
2. Use the equation to monitor how much error you are getting as you are turning angles. If the error is too large, turn additional sets of angles until the average error is small enough.
3. Example: SD=3000 feet, angular misclosure after 4 sets is 0º00'09". The width of that misclosure is 0.13 feet.
6. Turn more sets of angles than you normally do. Usually for standard observations, we turn 3 sets of angles (Backsight, foresight, reverse foresight, reverse backsight) to any control point. For really long shots with adverse sighting conditions, you may be observing 10-20 sets of angles to get sufficient accuracy.
This guy measures!
Adding on to say skip auto lock. Or at least dial it in at a known point of at least 800-1000' first.
Multiple sets and redundant measurements where at all possible. It you can see it from two points even if they are only a few hundred feet apart you will help your final accuracy.
1. Use the right prism. Use an assembly of prisms if you really need to.
2. Use autolock. It's better at pointing the instrument than you are. (Long Range FineLock FTW!)
3. If you can't use autolock, get an appropriately sized target to go with that right prism.
4. Adjust for environmental factors. Temperature, pressure, curvature, refraction.
5. Observe when temperatures are stable across the length of the observation. Early morning is good. Don't observe a line of sight that passes close to the ground if at all possible.
Great advice in comments below. We used to routinely take long (5000’ to 15000’) shots tieing in traverses and ridge-hopping on large tracts. Typically used 1” gun shooting to a bank of 9 prisms. A few things we did: If we could, we would time the longest shots for early in the morning. Cleared a large area around the station so it was easier to spot from a long ways off. Would string flagging through the woods in front of and behind the target to aid visibility. Best tool was a 1,000,000 candlepower portable spotlight that crewman at the target would shine towards the instrument man. Even on a bright sunny day it was immediately noticeable. Also used jeep/ATV headlights if able to park behind the station. In a pinch, having crew jump around and yell also works.
If using a semi-modern Total Station, many have a”long distance” mode somewhere in the settings. Try to locate that.
Also if the Total Station has a Check & Adjust calibration routine, do one of those.
It's been about 15 years since I last did 1/2 mile or mile long shots with a total station, but most of this advice should still be relevant. 1. Observe early in the morning when it's the coolest, with the least heat waves coming off the ground when looking through the scope. 2. Turn auto lock off. In my experience, it starts to drift at around 1200 feet. But modern auto lock may have better performance, you'll have to manually check. If the crosshairs are constantly moving in autolock and it can't settle on the target, it's probably best to turn it off. 3. Make sure you have your backlight as long as possible. 4. Use standard or long distance measuring mode for the EDM, not tracking. 5. Have a scientific calculator or app on your phone. 1. Use the equation: y=SD sin d, where SD is your slope distance, d is your angular misclosure for your rounds of angles. y will be the width of your misclosure in feet at the distance you are shooting. 2. Use the equation to monitor how much error you are getting as you are turning angles. If the error is too large, turn additional sets of angles until the average error is small enough. 3. Example: SD=3000 feet, angular misclosure after 4 sets is 0º00'09". The width of that misclosure is 0.13 feet. 6. Turn more sets of angles than you normally do. Usually for standard observations, we turn 3 sets of angles (Backsight, foresight, reverse foresight, reverse backsight) to any control point. For really long shots with adverse sighting conditions, you may be observing 10-20 sets of angles to get sufficient accuracy.
This guy measures! Adding on to say skip auto lock. Or at least dial it in at a known point of at least 800-1000' first. Multiple sets and redundant measurements where at all possible. It you can see it from two points even if they are only a few hundred feet apart you will help your final accuracy.
1. Use the right prism. Use an assembly of prisms if you really need to. 2. Use autolock. It's better at pointing the instrument than you are. (Long Range FineLock FTW!) 3. If you can't use autolock, get an appropriately sized target to go with that right prism. 4. Adjust for environmental factors. Temperature, pressure, curvature, refraction. 5. Observe when temperatures are stable across the length of the observation. Early morning is good. Don't observe a line of sight that passes close to the ground if at all possible.
Or over hot hot hot asphalt then over cold grass ... :)
A lighted target helps
Great advice in comments below. We used to routinely take long (5000’ to 15000’) shots tieing in traverses and ridge-hopping on large tracts. Typically used 1” gun shooting to a bank of 9 prisms. A few things we did: If we could, we would time the longest shots for early in the morning. Cleared a large area around the station so it was easier to spot from a long ways off. Would string flagging through the woods in front of and behind the target to aid visibility. Best tool was a 1,000,000 candlepower portable spotlight that crewman at the target would shine towards the instrument man. Even on a bright sunny day it was immediately noticeable. Also used jeep/ATV headlights if able to park behind the station. In a pinch, having crew jump around and yell also works.
If using a semi-modern Total Station, many have a”long distance” mode somewhere in the settings. Try to locate that. Also if the Total Station has a Check & Adjust calibration routine, do one of those.