Where does the Geoid information in a GPS unit come from?
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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
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asked Nov 28 at 15:29
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up vote
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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
10k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
New contributor
Håkon K. Olafsen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
up vote
3
down vote
favorite
up vote
3
down vote
favorite
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
10k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
New contributor
Håkon K. Olafsen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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
10k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
New contributor
Håkon K. Olafsen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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edited Nov 28 at 15:42
Dan C
10k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
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Håkon K. Olafsen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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edited Nov 28 at 15:42
Dan C
10k74575
edited Nov 28 at 15:42
Dan C
10k74575
edited Nov 28 at 15:42
Dan C
10k74575
10k74575
asked Nov 28 at 15:29
Håkon K. Olafsen
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asked Nov 28 at 15:29
Håkon K. Olafsen
1163
asked Nov 28 at 15:29
Håkon K. Olafsen
1163
1163
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Håkon K. Olafsen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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2 Answers
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5
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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
10k74575
add a comment |
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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
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Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
add a comment |
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
5
down vote
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
10k74575
add a comment |
up vote
5
down vote
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
10k74575
add a comment |
up vote
5
down vote
up vote
5
down vote
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
10k74575
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
10k74575
edited yesterday
answered Nov 28 at 15:58
Dan C
10k74575
answered Nov 28 at 15:58
Dan C
10k74575
answered Nov 28 at 15:58
Dan C
10k74575
10k74575
add a comment |
add a comment |
up vote
1
down vote
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
1113
New contributor
hobbs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
add a comment |
up vote
1
down vote
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
1113
New contributor
hobbs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
add a comment |
up vote
1
down vote
up vote
1
down vote
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
1113
New contributor
hobbs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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
1113
New contributor
hobbs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited Nov 29 at 0:51
answered Nov 28 at 20:18
hobbs
1113
New contributor
hobbs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
answered Nov 28 at 20:18
hobbs
1113
answered Nov 28 at 20:18
hobbs
1113
1113
New contributor
hobbs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
hobbs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
hobbs is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
add a comment |
Can you clarify whether you mean EGM84 or EGM96?
– mkennedy
Nov 29 at 0:37
@mkennedy sorry, corrected. 96. Unless it's terribly old equipment, of course :)
– hobbs
Nov 29 at 0:52
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
@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
add a comment |
Håkon K. Olafsen is a new contributor. Be nice, and check out our Code of Conduct.
Håkon K. Olafsen is a new contributor. Be nice, and check out our Code of Conduct.
Håkon K. Olafsen is a new contributor. Be nice, and check out our Code of Conduct.
Håkon K. Olafsen is a new contributor. Be nice, and check out our Code of Conduct.
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