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] <mailto:[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] <mailto:[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]
<mailto:[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]
<mailto:[email protected]>> *On Behalf Of *Steve Jones
*Sent:* Monday, December 28, 2020 11:44 AM
*To:* AnimalFarm Microwave Users Group <[email protected]
<mailto:[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] <mailto:[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]
<mailto:[email protected]>> *On Behalf Of *Steve
Jones
*Sent:* Monday, December 28, 2020 10:41 AM
*To:* AnimalFarm Microwave Users Group
<[email protected] <mailto:[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] <mailto:[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]
<mailto:[email protected]>> wrote:
Have any of you guys ever had the FCC verify
your transmitter data?
What equipment do they use to verify elevation
and coordinate?
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