On a RtN with rover. State plane projection, using a geoid (CRTN, SPCS NAD83, zone 6, geoid 18)
had a project by the ocean. Half day deal today.
experimenting with the gps on CRTN, and hit a BM with it. Wanted to get used to setting up and connecting. Getting familiar with the equipment, etc
While it showed “fixed”, 1sec corrections, all other parameters good, we’re exactly 2’ low of BM.
ok. That’s no problem. It’s gps, it’s on a RTN. There’s a lot I don’t know yet.
okay, so we walk away to a new area, it’s in float mode now. Walk it back to the BM and it hits exactly on the elevation. Still in float mode.
as we let it sit, it goes into “fixed” mode, and it “corrects” to 2’ low again.
we had to laugh. Float was “better” than fixed.
i know there’s a lot going on here. I’m just trying to wrap my head around that.
is there a book or reference material I can read to be able to understand this?
go easy on me - I’m a LSIT - it’s in the name - “in training”.
I’ve been reading/studying sickle’s gps for surveyors. Datum’s, origins, reference ellipsoids. Ellipsoidal vs geoidal vs or pho heights. Etc
im beginning to grasp it all. But just was curious what someone’s immediate thoughts were on as to why once it became “fixed”, it would set me 2’ low of a published county benchmark referenced to navd88, and when I lose lock “float” I’m hitting right on.
Thanks for any info or direction to reference materials