NAVD29

NGVD29
NAVD88

Carry on...

sure. go ahead. there is no such thing.....

In order to use NGVD29 you would need to tie at least one NGVD29 benchmark (i.e. marks with PUBLISHED NGVD29 values). Four surrounding your project would be better, depending on size. Then "calibrate" to those mark(s). You can use GEOID12A, but if you don't have any known elevations in your network then you are on (or close to) NAVD88.

to answer your original question, there is no "add-on" (geoid model) available to go from GRS80 ellipsoidal heights to NGVD29.

John Hamilton, post: 327403, member: 640 wrote: In order to use NGVD29 you would need to tie at least one NGVD29 benchmark (i.e. marks with PUBLISHED NGVD29 values). Four surrounding your project would be better, depending on size. Then "calibrate" to those mark(s). You can use GEOID12A, but if you don't have any known elevations in your network then you are on (or close to) NAVD88.

who publishes NAVD29 values? Not NGS or any County or City in Florida that I have ever seen. Maybe it's different up North.

PLS30820, post: 327408, member: 1439 wrote: who publishes NAVD29 values? Not NGS or any County or City in Florida that I have ever seen. Maybe it's different up North.

Many of the flood maps up this way are still referenced to NGVD29.

I recently had a request to convert data to NGVD 1929 for approval since the flood maps are still in 29. I guess they haven't had a chance to convert to the "new" datum yet. It hasn't quite been 30 years yet....

PLS30820, post: 327408, member: 1439 wrote: who publishes NAVD29 values? Not NGS or any County or City in Florida that I have ever seen. Maybe it's different up North.

The https://en.wikipedia.org/wiki/Washington_Suburban_Sanitary_Commission&apos ;">Washington Suburban Sanitary Commission, who run the public water and sewer system in the Maryland suburbs of DC still use 29 rather than try and convert data going back to the 1920's

PLS30820, post: 327408, member: 1439 wrote: who publishes NAVD29 values? Not NGS or any County or City in Florida that I have ever seen. Maybe it's different up North.

I've just had two new sets of subdivision construction plans come accross my desk this morning, both of which are referenced to NGVD 29!

B-)

PLS30820, post: 327408, member: 1439 wrote: who publishes NAVD29 values? Not NGS or any County or City in Florida that I have ever seen. Maybe it's different up North.

Central Florida here.

I currently have more NGVD29 (construction) jobs than NAVD88, but it is changing fast.

PLS30820, post: 327408, member: 1439 wrote: who publishes NAVD29 values? Not NGS or any County or City in Florida that I have ever seen. Maybe it's different up North.

In the Portland Metro Area there is:

• Clark County, Washington
• City of Vancouver, WA
• Washington County, Oregon

and the City of Portland has it's own elevation datum which is neither NAVD88 nor NGVD29.

But wait, are we talking NGVD29 OR NGVD29(47)?

PLS30820, post: 327408, member: 1439 wrote: who publishes NAVD29 values? Not NGS or any County or City in Florida that I have ever seen. Maybe it's different up North.

You can find them on many NGS data sheets under superceded values

Hijack alert...
We just performed a monitoring project with legacy vertical data. Our new work brought the absolute to NAVD88 using GPS. The only realistic option was OPUS and Geoid 12A.
For giggles I ran the old benchmark through vertcon. NGVD matched published 0.001'. I let it slide and held published. I also bought a lottery ticket.

Its certainly a mystery to me why people/agencies continue to use a system that has been obsolete for nearly 90 years. I'm glad I'll be retired by the time NSRS22 (or whatever they decide to call it) is published!

We work in a few towns that still require benchmarks on the 29 datum...but only b/c the people making the regulations have no concept of what a vertical datum is, and wouldn't care if you told them anyway.

-V

look at the first post. [hl]READ it[/hl]. he says "NAVD29", NOT "NGVD29"

Norman Oklahoma, post: 327416, member: 9981 wrote: In the Portland Metro Area there is:

• Clark County, Washington
• City of Vancouver, WA
• Washington County, Oregon

and the City of Portland has it's own elevation datum which is neither NAVD88 nor NGVD29.

really? The question was can he use NAVD29, not NGVD29...... The city of Miami has its own datum as well, so you have to convert from NAVD88 to it.

RFB, post: 327415, member: 142 wrote: Central Florida here.

I currently have more NGVD29 (construction) jobs than NAVD88, but it is changing fast.

Yeah, us too on the East Coast. The question is not about NGVD29 or NAVD88... You made that clear in your first post