[PROJ] Sweref99 Cartesian

[Roger Oberholtzer]

On Thu, Apr 21, 2022 at 9:39 AM Jivall Lotti <Lotti.Jivall at lm.se> wrote:

> Hi Roger,
>
> SWEREF 99 is a 3D geodetic reference system (the Swedish realisation of
> ETRS89) and can be expressed as geocentric cartesian coordinates (X Y Z) ,
> geodetic coordinates (latitude, longitude and height) or a number of map
> projections where SWEREF 99 TM is the national one (whole Sweden in one
> zone). You can read more at Lantmäteriets webb page
> <https://www.lantmateriet.se/en/maps-and-geographic-information/gps-geodesi-och-swepos/Referenssystem/Tredimensionella-system/SWEREF-99/>.
>
>
>
>
> You are right that SWEPOS virtual RINEX generator is requesting SWEREF 99
> XYZ (and I understand it might be easier for you to use PROJ instead of out
> online transformation on the webb). All SWEPOS services are producing data
> in SWEREF 99, as this is the national reference frame. It means that when
> you process your GNSS-observations with the VRS reference data then you
> will get the results in SWEREF 99. (Therefore you should *not* use the
> accurate NKG-transformation from  ITRF2014 (WGS84) to SWEREF 99 – if your
> final results should be presented in SWEREF 99!)
>
>
>
> Your original position from the GNSS-receiver is in WGS84 (current epoch)
> but I guess just on a few meter level and actually you just need a very
> approximate position to get your virtual reference near your own
> measurements. The position you input to SWEPOS VRS generator will be
> interpreted as SWEREF 99.
>
>
>
> Hope it is now more clear!
>

I think so. So you mean if I provide the receiver's WGS84 lat/lng to, say,  cct
+proj=cart +ellps=GRS80 , then the resulting locations should be adequate
for requesting a virtual station at that WGS84 location?

-- 
Roger Oberholtzer
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