Where does the Geoid information in a GPS unit come from?
In the NMEA GGA-message the 11th field is Geoid separation. How does the GPS-unit "know" this separation?
Are GPS units preloaded with an EGM (Earth Gravitational Model)?
gps nmea geoid
edited Nov 28 at 15:42
Dan C
10.1k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
add a comment |
In the NMEA GGA-message the 11th field is Geoid separation. How does the GPS-unit "know" this separation?
Are GPS units preloaded with an EGM (Earth Gravitational Model)?
gps nmea geoid
edited Nov 28 at 15:42
Dan C
10.1k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
add a comment |
In the NMEA GGA-message the 11th field is Geoid separation. How does the GPS-unit "know" this separation?
Are GPS units preloaded with an EGM (Earth Gravitational Model)?
gps nmea geoid
edited Nov 28 at 15:42
Dan C
10.1k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
In the NMEA GGA-message the 11th field is Geoid separation. How does the GPS-unit "know" this separation?
Are GPS units preloaded with an EGM (Earth Gravitational Model)?
gps nmea geoid
gps nmea geoid
edited Nov 28 at 15:42
Dan C
10.1k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
edited Nov 28 at 15:42
Dan C
10.1k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
edited Nov 28 at 15:42
Dan C
10.1k74575
edited Nov 28 at 15:42
Dan C
10.1k74575
edited Nov 28 at 15:42
Dan C
10.1k74575
10.1k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
1163
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
GPS units can be pre-loaded with one or more geoids, which can be used to calculate elevations by geoid separation. But support for this feature varies by manufacturer and by device.
On many Trimble GPS units (and probably units from other manufacturers who make higher-end GNSS hardware for professional surveying), the geoid is stored on the device. Trimble uses a .GGF file. You can add new geoids and decide which one your unit will use. Geoids can be refined over time so the ability to add new ones helps keep your hardware up to date.
When it comes to a consumer GPS handheld like a Garmin or whatever, my guess is that they have one geoid and/or ellipsoid (another abstraction of the earth's surface that is used to calculation elevations) pre-loaded on the device which can't be updated. But you'd need to check the specs for your device and maybe contact the manufacturer to find out for sure.
answered Nov 28 at 15:58
Dan C
10.1k74575
add a comment |
Unless otherwise specified, a GPS unit is probably using the WGS84 ellipsoid and EGM96 geoid, and the separation it reports is the vertical distance between those two surfaces at the present latitude and longitude. Yes, it's usual to have that data baked into the firmware.
answered Nov 28 at 20:18
hobbs
1213
2
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
1
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
1
Do you have any source for this? I don't doubt you, but it would be handy for future reference and reading.
– Håkon K. Olafsen
Dec 3 at 11:34
add a comment |
Your Answer
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "79"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fgis.stackexchange.com%2fquestions%2f304256%2fwhere-does-the-geoid-information-in-a-gps-unit-come-from%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
GPS units can be pre-loaded with one or more geoids, which can be used to calculate elevations by geoid separation. But support for this feature varies by manufacturer and by device.
On many Trimble GPS units (and probably units from other manufacturers who make higher-end GNSS hardware for professional surveying), the geoid is stored on the device. Trimble uses a .GGF file. You can add new geoids and decide which one your unit will use. Geoids can be refined over time so the ability to add new ones helps keep your hardware up to date.
When it comes to a consumer GPS handheld like a Garmin or whatever, my guess is that they have one geoid and/or ellipsoid (another abstraction of the earth's surface that is used to calculation elevations) pre-loaded on the device which can't be updated. But you'd need to check the specs for your device and maybe contact the manufacturer to find out for sure.
answered Nov 28 at 15:58
Dan C
10.1k74575
add a comment |
GPS units can be pre-loaded with one or more geoids, which can be used to calculate elevations by geoid separation. But support for this feature varies by manufacturer and by device.
On many Trimble GPS units (and probably units from other manufacturers who make higher-end GNSS hardware for professional surveying), the geoid is stored on the device. Trimble uses a .GGF file. You can add new geoids and decide which one your unit will use. Geoids can be refined over time so the ability to add new ones helps keep your hardware up to date.
When it comes to a consumer GPS handheld like a Garmin or whatever, my guess is that they have one geoid and/or ellipsoid (another abstraction of the earth's surface that is used to calculation elevations) pre-loaded on the device which can't be updated. But you'd need to check the specs for your device and maybe contact the manufacturer to find out for sure.
answered Nov 28 at 15:58
Dan C
10.1k74575
add a comment |
GPS units can be pre-loaded with one or more geoids, which can be used to calculate elevations by geoid separation. But support for this feature varies by manufacturer and by device.
On many Trimble GPS units (and probably units from other manufacturers who make higher-end GNSS hardware for professional surveying), the geoid is stored on the device. Trimble uses a .GGF file. You can add new geoids and decide which one your unit will use. Geoids can be refined over time so the ability to add new ones helps keep your hardware up to date.
When it comes to a consumer GPS handheld like a Garmin or whatever, my guess is that they have one geoid and/or ellipsoid (another abstraction of the earth's surface that is used to calculation elevations) pre-loaded on the device which can't be updated. But you'd need to check the specs for your device and maybe contact the manufacturer to find out for sure.
answered Nov 28 at 15:58
Dan C
10.1k74575
GPS units can be pre-loaded with one or more geoids, which can be used to calculate elevations by geoid separation. But support for this feature varies by manufacturer and by device.
On many Trimble GPS units (and probably units from other manufacturers who make higher-end GNSS hardware for professional surveying), the geoid is stored on the device. Trimble uses a .GGF file. You can add new geoids and decide which one your unit will use. Geoids can be refined over time so the ability to add new ones helps keep your hardware up to date.
When it comes to a consumer GPS handheld like a Garmin or whatever, my guess is that they have one geoid and/or ellipsoid (another abstraction of the earth's surface that is used to calculation elevations) pre-loaded on the device which can't be updated. But you'd need to check the specs for your device and maybe contact the manufacturer to find out for sure.
answered Nov 28 at 15:58
Dan C
10.1k74575
edited Nov 30 at 17:10
answered Nov 28 at 15:58
Dan C
10.1k74575
answered Nov 28 at 15:58
Dan C
10.1k74575
answered Nov 28 at 15:58
Dan C
10.1k74575
10.1k74575
add a comment |
add a comment |
Unless otherwise specified, a GPS unit is probably using the WGS84 ellipsoid and EGM96 geoid, and the separation it reports is the vertical distance between those two surfaces at the present latitude and longitude. Yes, it's usual to have that data baked into the firmware.
answered Nov 28 at 20:18
hobbs
1213
2
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
1
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
1
Do you have any source for this? I don't doubt you, but it would be handy for future reference and reading.
– Håkon K. Olafsen
Dec 3 at 11:34
add a comment |
Unless otherwise specified, a GPS unit is probably using the WGS84 ellipsoid and EGM96 geoid, and the separation it reports is the vertical distance between those two surfaces at the present latitude and longitude. Yes, it's usual to have that data baked into the firmware.
answered Nov 28 at 20:18
hobbs
1213
2
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
1
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
1
Do you have any source for this? I don't doubt you, but it would be handy for future reference and reading.
– Håkon K. Olafsen
Dec 3 at 11:34
add a comment |
Unless otherwise specified, a GPS unit is probably using the WGS84 ellipsoid and EGM96 geoid, and the separation it reports is the vertical distance between those two surfaces at the present latitude and longitude. Yes, it's usual to have that data baked into the firmware.
answered Nov 28 at 20:18
hobbs
1213
Unless otherwise specified, a GPS unit is probably using the WGS84 ellipsoid and EGM96 geoid, and the separation it reports is the vertical distance between those two surfaces at the present latitude and longitude. Yes, it's usual to have that data baked into the firmware.
answered Nov 28 at 20:18
hobbs
1213
edited Nov 29 at 0:51
answered Nov 28 at 20:18
hobbs
1213
answered Nov 28 at 20:18
hobbs
1213
answered Nov 28 at 20:18
hobbs
1213
1213
2
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
1
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
1
Do you have any source for this? I don't doubt you, but it would be handy for future reference and reading.
– Håkon K. Olafsen
Dec 3 at 11:34
add a comment |
2
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
1
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
1
Do you have any source for this? I don't doubt you, but it would be handy for future reference and reading.
– Håkon K. Olafsen
Dec 3 at 11:34
2
2
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
1
1
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
1
1
Do you have any source for this? I don't doubt you, but it would be handy for future reference and reading.
– Håkon K. Olafsen
Dec 3 at 11:34
Do you have any source for this? I don't doubt you, but it would be handy for future reference and reading.
– Håkon K. Olafsen
Dec 3 at 11:34
add a comment |
Thanks for contributing an answer to Geographic Information Systems Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fgis.stackexchange.com%2fquestions%2f304256%2fwhere-does-the-geoid-information-in-a-gps-unit-come-from%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
