Well, at least we had mirrors. From: Tim Hardy Sent: Monday, December 28, 2020 3:01 PM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] FCC coordinate verification
Heck, when we were laying out the MCI system in 1971, the best maps in most area were 1:250,000 - and some areas out west, even worse than that. Try getting accurate anything at those scales, particularly when the contour granularity was up to 250’! On Dec 28, 2020, at 3:13 PM, Chuck McCown via AF <[email protected]> wrote: I remember putting scale marks on a rubber band and literally stretching it to get interpolated elevation contours. I also used to do path profiles with curved graph paper laying on the floor. The amount of data precision on FCC applications has to be an order of magnitude better than it was 30 years ago. But it was good enough for them back then. From: Adam Moffett Sent: Monday, December 28, 2020 12:24 PM To: [email protected] Subject: Re: [AFMUG] FCC coordinate verification One of the earliest US state borders was laid out by placing stone pillars every mile or so by taking measurements off the stars. That was literally good enough for government work. One of our founding fathers personally surveyed that. Up until the 1990's anybody doing this must have been using a compass and a ruler on a paper printout of a topo quad. I remember as a draftsman in 1997 taking measurements off an old site plan to draw a new site plan, and telling the engineer we would be within +/- 3 feet. His eyes popped out a bit, but then I explained that on the drawing we're working with 1/64" is 3 feet wide and I literally can't measure closer than that with a ruler. The best part was we had raw survey data for the property lines and when I drew them out in AutoCAD the western edge of the property was made of two lines that passed each other. When I measured closely on the old drawing it was clear the previous draftsman had drawn both non-intersecting lines and then blurred them together with his pencil.....so I did basically the same thing in AutoCAD. They rebuilt a sewage treatment plant with a site plan where any given building might have been 3 feet out of position and the official property line was a smudge mark. The builders figured out what to do just fine. My point is, I think if you take your best effort at measuring coordinates and heights with today's tools then you did ok and it's not necessary to fuss over it too hard. On 12/28/2020 1:56 PM, Mathew Howard wrote: Yeah, I have no idea. It seems a little pointless to have to worry about being within 3 feet for agl if you don't have an accurate ground level. I wonder how accurate you can actually get with ground levels, and what the most accurate method for determining it is. On Mon, Dec 28, 2020 at 12:52 PM Steve Jones <[email protected]> wrote: we use a trupulse for agl, but even with agl being accurate at that slice in time, is the ground level accurate? On Mon, Dec 28, 2020 at 12:35 PM Mathew Howard <[email protected]> wrote: I always figured that using Google Earth for lat/lon and ground elevation is as accurate as I'm going to realistically get with any method that's available to me (yeah, I suppose I could pay a surveyor to go out there and get me better numbers, but that's not really going to happen). As long as I check a few points around the area and don't find any drastic (unexpected) differences in elevation, I figure it's pretty accurate. Making a mistake in mounting height on the tower seems like a bigger concern to me... on smaller towers, I should be able to get within a few inches by counting tower sections, or even dropping a tape measure, but if you're up a few hundred feet, that can get a lot trickier. On Mon, Dec 28, 2020 at 12:07 PM Ken Hohhof <[email protected]> wrote: IANAL but if I wanted to do an audit, I’d just check against Google Earth for lat/lon and ground elevation. That’s close enough nobody will care about the difference. For azimuth, if you have the lat/lon of each end, you can calculate azimuth, assuming the antennas were aligned properly. If the RSSI is within a few dB of target, they were aligned properly. You can find azimuth by drawing a line on Google Earth, or using something like LinkPlanner. I’d mostly be worried about xmt freq, channel width, and xmt power matching the license. It would be easy to miss the fact that frequency coordination showed you needed to dial back the xmt power, or to make a mistake and be on the wrong frequency. Those would be bad errors. Tougher one to audit would be AGL. You coordinate the link, apply for your license, then tell the tower guys to mount the dish at 100 feet. But how do they determine 100 feet? Count tower sections? Foot markers on cable? Tape drop? Laser rangefinder? Maybe there’s a beacon light at the 100 feet so they put it at 90 or 110. Or there’s a nice abandoned mount at 120 feet so they put it there. From: AF <[email protected]> On Behalf Of Steve Jones Sent: Monday, December 28, 2020 11:44 AM To: AnimalFarm Microwave Users Group <[email protected]> Subject: Re: [AFMUG] FCC coordinate verification hypothetical, If FCC was coming I would be freaking out. I just spend a lot of time nervous about all our licensed links and one day finding out we are just outside the margin, particularly on amsl. We use the smart aligner now to verify the coordinate, but I assume FCC has more accurate meter than me. Or I'm completely off and FCC equates to whoever FCC contract to come. I can look at tolerance charts all day, but If I dont know what the tolerance is measured against, what value is it. Like if I want to get super accurate on weights I can go steal one of the ones in the jars and compare it to my weights On Mon, Dec 28, 2020 at 11:02 AM Ken Hohhof <[email protected]> wrote: When I had our frequency coordinator do an FAA application for us (licensed link on tower near airport) and mentioned the discussion here about 2C surveys, they acted like I was crazy. Are you sure this is required? Steve, is this hypothetical, or is the FCC paying you a visit? I know one time I discovered the commercial tower we were on had the lat/lon wrong on the ASR. For us to fix out license, they had to also fix the ASR. It was just a matter of filing a modification. I also seem to remember something about it wasn’t significant unless it was off by at least 1 second or something. Honestly I just use the numbers from my Garmin 64st, same as for CPI data for CBRS. Given several minutes it will usually state accuracy within <10 feet. I check it against Google Earth and they usually match to better than that. Even the elevation AMSL usually matches. If there was a need for a survey I would think it would have to be for AMSL, there’s just no rational reason to need a surveyor to certify the lat/lon these days. From: AF <[email protected]> On Behalf Of Steve Jones Sent: Monday, December 28, 2020 10:41 AM To: AnimalFarm Microwave Users Group <[email protected]> Subject: Re: [AFMUG] FCC coordinate verification im asking about if you get nailed by the FCC, not application On Mon, Dec 28, 2020 at 10:13 AM Cameron Crum <[email protected]> wrote: Typically if you are filing for FAA or FCC you have to supply coordinates from a 2C survey mimium. They assume a certified survey is good enough. On Mon, Dec 28, 2020 at 10:02 AM Steve Jones <[email protected]> wrote: Have any of you guys ever had the FCC verify your transmitter data? 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