Yes: for several years we used differential GPS at our airfield. The GPS in
the ATC tower was checked against the exact position and the difference
transmitted to the GPS units in our aircraft. We no longer have the
differential station but the airborne units continue to work fine.
Chris
> On 26 Apr 16, at 11:28, Chris Weir <chris.a.weir@xxxxxxxxx> wrote:
>
> The "selective availability" that reduced the accuracy of civilian GPS was
> removed a fair while ago. Due to the use of many civilian units by the
> military selective availability had to be turned off before large
> operations which was a bit of a give away - so it was turned off
> permanently. I recall this occurring as we were suddenly getting much more
> accurate fixes on the equipment I was developing at the time.
>
> Chris
>
> On Tue, Apr 26, 2016 at 7:29 AM, Ken Norton <ken@xxxxxxxxxxx
> <mailto:ken@xxxxxxxxxxx>> wrote:
>
>> If you are in a canyon or some place where you are getting visibility
>> to not enough satellites, the accuracy will diminish a little.
>> Otherwise, your assumption is correct that the vertical offset will
>> remain the same.
--
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