Geotagging is great for photographers who like to share with fellow photographic enthusiasts exactly where they captured a specific image, so others can find that spot and make their own images of the same subject. We also know a few photographers who like to keep their favorite shooting spots a secret and won't divulge the GPS coordinates of these locations!
Nikon
DSLR Camera are commonly deliver with a 10-pin remote terminal, are
capable of automatically writting geo-refferential meta-data into image
headers (Exif), known as "geo-tagging".
Balanced lines are recommended but the standard also allows the simple RS232-level signals which Nikon uses. Asynchronous serial communications is performed with no handshake at 4800 bauds, 8 data bits (bit 7 being 0) no parity and one stop bit.
This picture below show Icon "GPS" indicating that the GPS is connected. (top screen of the Nikon D800).
In the "Setup Menu" - "GPS" - "Position" of the camera, the last position, Altitude, Heading, and the current UTC from the GPS satellites time are displayed. You can choose to automatically sync the camera to the GPS time in the menu.
Vectornav VN-200 have an internal 3-axis Compass, so the heading information is provided into display. The 3-axis Compass provides accurate data even when tilted to various angles of all 3-axis.
Nikon would be able to display and record Heading information to the EXIF header if they receive NMEA data with a "$HCHDG" prefix sentences.
HCHDG - Compass output is used on Garmin
etrex summit, vista , and 76S receivers to output the value of the internal
flux-gate compass. Only the magnetic heading and magnetic variation is shown in
the message.
$HCHDG,101.1,,,7.1,W*3C
where:
HCHDG Magnetic heading,
deviation, variation
101.1 heading
,, deviation (no data)
7.1,W variation
HDG Heading–Deviation and
Variation
1 2 3 4 5 6
| | | | | |
$--HDG,x.x,x.x,a,x.x,a*hh
1) Magnetic Sensor heading in
degrees
2) Magnetic Deviation, degrees
3) Magnetic Deviation direction, E =
Easterly, W = Westerly
4) Magnetic Variation degrees
5) Magnetic Variation direction, E =
Easterly, W = Westerly
6) checksum
User can also adding heading, pitch and roll (HPR) information to the EXIF header, but these information were not displayed into the Camera. User can read this information using software EXIF reader. This could be done if NIKON Camera receive NMEA data with a "$PTNTHPR" prefix sentences.
HPR Transducer Measurements (proprietary data)
1 2 3 4 5 6 7| | | | | | |$PTNTHPR,x.x,a,x.x,a,x.x,a*hh1)Heading2)N for Number3)Pitch in degrees4)N for Number5)Roll in degrees6)N for Number7)checksum
To display and record Lattitude, Longitude, Altitude, and the current UTC from the GPS satellites time information to the EXIF header if NIKON Camera receive NMEA data with a "$GPRMC" and "$GPGGA" prefix sentences.
GGA - essential fix data which provide
3D location and accuracy data.
$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
Where:
GGA Global Positioning
System Fix Data
123519 Fix taken at 12:35:19
UTC
4807.038,N Latitude 48 deg
07.038' N
01131.000,E Longitude 11 deg
31.000' E
1 Fix quality: 0 =
invalid
1 = GPS fix
(SPS)
2 = DGPS fix
3 = PPS fix
4 = Real Time Kinematic
5 = Float RTK
6 = estimated (dead reckoning) (2.3 feature)
7 = Manual input mode
8 = Simulation mode
08 Number of satellites
being tracked
0.9 Horizontal dilution
of position
545.4,M Altitude, Meters,
above mean sea level
46.9,M Height of geoid (mean
sea level) above WGS84
ellipsoid
(empty field) time in seconds since last DGPS update
(empty field) DGPS station ID number
*47 the checksum data,
always begins with *
If the height of geoid is missing
then the altitude should be suspect. Some non-standard implementations report
altitude with respect to the ellipsoid rather than geoid altitude. Some units
do not report negative altitudes at all. This is the only sentence that reports
altitude.
RMC - NMEA has its own version of essential gps pvt (position, velocity, time) data. It is called RMC, The Recommended Minimum, which will look similar to:
RMC - NMEA has its own version of essential gps pvt (position, velocity, time) data. It is called RMC, The Recommended Minimum, which will look similar to:
$GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A
Where:
RMC Recommended Minimum
sentence C
123519 Fix taken at 12:35:19
UTC
A Status A=active or
V=Void.
4807.038,N Latitude 48 deg
07.038' N
01131.000,E Longitude 11 deg
31.000' E
022.4 Speed over the ground
in knots
084.4 Track angle in
degrees True
230394 Date - 23rd of March
1994
003.1,W Magnetic Variation
*6A The checksum data,
always begins with *
At least NIKON Camera receive NMEA data with 3 prefix sentences, $GPGGA, $GPRMC, "$HCHDG" for geotagging images. Below the examples of streaming NMEA data from GPS to NIKON Camera.
Keywords: Geotagging, geo-tagging, Nikon, DSLR, D800, D810, Heading, NMEA, $GPGGA, $GPRMC, $HCHDG, $PTNTHPR, Exif header, VN-200, Vectornav.
