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Successful Field Procedures

Operationally the ScanLook system is very easy to use. How to plug it in and operate it has all been discussed in other areas. However, it takes more than just knowing how to use the system to successfully get the job done right. Here are just a few hints.

Base Station Hints

Put your base station in an area with a clear view of the sky.

This generally means a clear view from 10 degrees above the horizon. Stay away from tall buildings, trees, high voltage power, and the possibility of blockage from intermittent traffic such as a train. You may need to use rooftop.

Use a known point.

In particular, your likelihood of success increases if you can use the same local benchmark as your client. Start from a common datum and common reference point. While you can derive point coordinates from your base station after a sufficiently long session, it is far better to start from the same physical point.

Log your base station at 1Hz or better.

Be sure to set your base station to log at 1Hz. While 5, 10, or more Hz will work, your solution will be degraded.

Set your base station within a reasonable distance from your project area.

Do not set your base station at the office and drive 50 miles to the project area. If possible, put your base station near the center of your project.

Log data before and after the mobile session.

The more data you have with your base station, the better. Get at least 5 or 10 minutes of data on both ends of your mobile collection if possible.

Check your base station power supply.

There's nothing to dampen a good day like finding out your base station ran out of battery power before the mobile mission completed. Test your system before hand with the settings you plan to use to see how long the system will really work. Be sure to start with a fully charged system. An external battery is almost always a good thing to add.

Make sure your base station has enough storage for your session.

Most base stations can collect for days but some older systems only have enough capacity for a few hours. Be sure to know the limits of your system and plan accordingly.

System Hints

Warm up your INS.

Turn the system on and let the INS warm up. Some systems require more time than others but allow at least a few minutes for this. Capturing data during this time also is not going to hurt as you can always clip it out in post processing. Let the system settle for at least a minute after collection (the reverse of the setup).

Start ScanLook in a clear area with good GPS coverage.

Be sure to obtain a good GPS lock before you begin scanning. This may mean driving a few blocks, maybe a mile, to get a good clear view of the sky long enough to gain GPS lock. Failing to do this drastically undermines the likelihood of a successful mission.

Excite the INS.

Exciting the INS is not always possible, particularly on a rail system but if possible it can be beneficial to make a right turn, left turn sequence to get the INS ready to work. It helps with the alignment in real-time and in post processing. Try to get over 5mph if possible. If scanning from a backpack or cart, a really brisk walk for about 30 seconds with a few sharp turns can be very helpful. This all of course depends upon the INS you are using.

Check your storage space.

Make sure each device has enough space to store the necessary data for the duration you plan on operating. Be sure to give yourself some room for extra data.

Secure all cables and connectors.

Use tape or zip ties to secure any over sized cables or straps. Make sure all cables are also securely fastened in place including any USB and ethernet ports you may be using.

Securely fasten the system in place.

This is without a doubt the most important piece of advice. You do not want to lose your system while traveling. It would be an outright disaster. Not only would your scan session be a failure, but this loss could cost you the project, your job, or your business. A little extra precaution goes a long way here.

Start your INS in the direction you will be traveling.

This sounds a bit odd but on a rail project, in particular, if you start your INS while the train is backing up it can cause some difficulty in processing later, especially if the field technician is not the same person doing the trajectory processing.

Initializing your INS Hints

Start moving in a forward direction. 

If you do move in a backward direction (e.g. if you are on a train) then definitely make a note of this. If you are doing a PPK solution, this will be important. It can cause your heading to flop like crazy.

Warm up your INS

Give you INS a few minutes to warm up before scanning. Some systems take longer than others but for sure they all like being warmed up.

Initialize your INS

Along with moving in the right direction, you should know what your particular INS prefers for initialization (and post mission 'initialization'). For some FOG units, you need to sit nearly perfectly still for a few minutes. For the more common MEMS systems (NovAtel SPAN-IGM-S1/A1 (STIM300/ADIS), Trimble APX-15, VectorNav VN-300, and InertialLabs systems) a 30 second straight line at a constant speed followed by a 90 degree turn is a good practice.

Flying Hints

These are just some common sense items to consider before and during flight.

Check all of your batteries.

Some UAV's will not let you fly if the batteries are not equally charged but some will. Be sure to do this check yourself.

Fly a cheap system first.

If you are in an unfamiliar location, fly the cheapest system you have first to make sure all things are good. This can include unexpected vertical objects (cell towers, poles, wires), magnetic interference (covered piles of iron ore, etc.), and potentially angry birds (yeah, they are curious and territorial).

Fly the system without the lidar briefly.

If you have changed ANYTHING (firmware update, new blades, high altitude blades, etc.), anything at all, fly the bird for at least 5 minutes with no instruments (expensive camera, lidar unit) to make sure all things are good.

successful_field_procedures.txt · Last modified: 2017/11/03 09:08 by jeff.fagerman