Jump to content

Below Sea-Level readings


dweebe

Recommended Posts

I was in New Orleans this last weekend for Mardi Gras and took my SporTrak Pro with me. When in the Garden District and French Quarter I got altitude readings of 0 feet but nothing below that. I thought these parts of New Orleans were a few feet below sea-level. Is that correct and has anyone gotten a below 0 altitude reading with a GPSr?

Link to comment

I believe that the lowest reading that the SporTrak (and the Meridian) will give is zero. No negative altitudes for some reason.

 

Plus... you didn't hold the GPS on the ground did you? It was probably up around chest level, just about zero feet above sea level.

 

Jamie

Link to comment

I was in Naw'leans last year and I brought my Legend with me for the trip. There were quite a few locations along Canal Street that registered as being below sea level. We stayed in the French Quarter and ventured over to the Garden District, but I didn't have my GPS with me at the time.

 

Man, now I am craving a Po' Boy from Mothers and a beignet from Cafe Du Monde icon_frown.gif

Link to comment

quote:
Originally posted by BusBoy:

I was in Naw'leans last year and I brought my Legend with me for the trip. There were quite a few locations along Canal Street that registered as being below sea level. We stayed in the French Quarter and ventured over to the Garden District, but I didn't have my GPS with me at the time.


Early version of eTrex OS wouldn't display sub-sea level readings. If your unit doesn't, you may need to upgrade.

 

3608_2800.gif

Link to comment

The first time I checked tracking on my computer after downloading when I had travelled through the tunnel from Manhattan to Queens in NYC, I read -35 feet or so where the toll both was. Funny I didn't see the toll collectors wearing scuba gear.

 

Then I realized the Vista had gotten the baromettric reading while under the river, but because satellite lock was lost, carried that reading to points outside the tunnel. It didn't correct itself until it locked on the satellites again further down the road.

 

Alan

Link to comment

There are lots of posts about this in the Yahoo meridian group; many users complain about magellan units not capable of showing below zero values;

up to now even in the newest firmware versions no correction; somebody cited "they did it for marine use, sailors fearing if the GPS shows under zero"?

Ed

Link to comment

quote:
Originally posted by Jamie Z:

Plus... you didn't hold the GPS on the ground did you? It was probably up around chest level, just about zero feet above sea level.


 

I have no clue whether or not the Magellans show readings below zero or not, but even if they did...

 

The SporTrack Pro has a vertical accuracy of 10 meters (32.81 feet). Placing your GPSr on the ground would not give you any better accuracy reading. You could be three stories up in your hotel room and get roughly the same altitude reading as if your GPSr were laying flat on the surface of the road. If New Orleans is only "a couple of feet" below sea level in parts, it may show up as zero, and your actual altitude may still be as much as 33 feet below sea level.

 

I would imagine that the barometric altimeters are the way to go if you're looking for true altitude readings.

Link to comment

Standard Positioning Service global average vertical accuracy is <=22m [~72 feet) @ 95% SIS and <=77m [~252 feet) worst case scenario so GPS altitude is not all that relevent.

 

Vertical accuracy is also more affected (for the worse) by latitude than horizontal error especially once one is above about 55 degrees N/S latitude where as the higher latitudes generally improve horizontal accuracy.

 

Cheers, Kerry.

 

I never get lost icon_smile.gif everybody keeps telling me where to go icon_wink.gif

Link to comment

quote:
Originally posted by Anders:

In Sweden, we have some of the largest iron ore mines in the world. They are down some 1000 meters below the earth level. Maybe I should go visit that place (it's 1300 km from here...) and see what the Vista says??

 

Anders


 

Don't forget to take a canary! icon_smile.gif

 

alan

Link to comment

I've seen it (falsely) report parts of cities like Helsingborg and Malmö to be several meters below sea level. Although they are at the coastline, they certainly aren't that wet. It (the Vista) gets a little confused now and then, obviously due to weather differences at different places.

 

Anders

Link to comment

quote:
Originally posted by Jamie Z:

Plus... you didn't hold the GPS on the ground did you? It was probably up around chest level, just about zero feet above sea level.


quote:
Originally posted by rag-a-muffin:

I have no clue whether or not the Magellans show readings below zero or not, but even if they did...


Yeah, yeah I know. I was a thinly disguised joke.

 

Jamie

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...