GeoBiking.Org - Glossary

GeoBiking Glossary

Barometer

Air Pressure Sensor

Barometric altimeters use air pressure to determine your altitude. So when the weather changes, so does your elevation.
Satellite elevation can therefore often be more accurate than one derrived from pressure and is typically within 100 feet w/o need for calibration
Some units allow you to use the GPS to set the barometer.
Any GPS can determine your elevation without having a barometer while you are receiving 4 or more satellites.
Vertical accuracy is typically twice the estimated position error,

Barometric Elevation

Altitude measured via air pressure change.

Unit must be calibrated at location it is powered on
Requires known elevation or pressure to calibrate
Changes as weather does
Some units allow you to calibrate automtically via GPS calculations

Contour Lines

Lines on a map having the same elevation

The closer the lines are together, the steeper the slope
To provide useful information, they should not be more than 50 elevation feet apart when zoomed in tight

Electronic Compass

Electronic Direction Sensor

Any GPS can show your speed and direction as long as you have reception and are moving: see "Satellite Compass".

Can be used when stopped
E-Compass accuracy is typically +/- 5 degrees or worse
Usually must be recalibrated each time you change batteries
Many require GPS to be held level for proper operation
"3-Axis compasses can still be used when tilted
Consume a noticeable amount of power.

Elevation

Distance above Sea Level - AKA Altitude

Can be determined via calculation from satellite signals (Satellite Altimeter) or via air pressure (Barometric Altimeter).
Barometric calculations can better reflect short term changes in altitude
Barometric calculations are subject to large changes caused by weather changes

{aliases altitude}

EPE

Estimated Position Error - an estimate of the accuracy of your position

This is only and estimate and is calculated differently between vendors/units
Accuracy is primarily determined by how well the satellites the GPS is using are spread
Strong reflected signals can negatively affect
Vertical accuracy is typically twice the estimated position error

GeoBiking

A popular use of handheld GPS - See this website for more information

A FREE outdoor GPS activity that helps you explore a hidden world nearby
A network of hundreds of trails covering >2,300 miles of trails
Viewable on GPS as tracklogs or map overlays on Garmin or DeLorme GPSr
Preview trails in Google Earth
Improve your health while enjoying mostly off street riding

Geocaching

A popular use of handheld GPS - See GPSmagazine for better description

An outdoor GPS game where you search for "treasure caches"
You can log your visit and exchange "trinkets"

Glonass

Russian Federation Global Position System

System is similar to our GPS system
21 satellites in 3 orbital planes with 3 in orbit spares
All Ground stations are within the former Soviet Union
Garmin Montana 610 & 680, Oregon 600 series, 64 series, Etrex 10, 20, 25, 30 & 35 can also use this system
With Garmin series above you can turn Glonass off to conserve some power
Using it should reduce lock on time 20%
Using both constellations will also improve accuracy because of improved satellite geometry

Google Earth

Application that supports viewing earth via aerial imagery

KML is the input/output for this application
Can read GPX format
Supports many types of data overlays
Supports 3D buildings
Allows "fly-bys" of "paths"
"Street View" allows ground level viewing
Can view underwater & moon too!

Google Maps

DIfferent mapping interface

Subset of Google Earth KML
Does not support controlling visibility of layers
Used for interactive mapping on GeoBiking.Org
Uses www.mappingsupport.com for viewing

GPS

Global Positioning System

A system of 24 active satellites that orbit the earth sending signals that allow a handheld receiver to triangulate it's location.
There are a couple spares aloft as well as some WAAS satellites that help correct for atmospheric anomalies
Signals from 4 satellites are required for a fix
However, if they are not well spread in the sky, accuracy will be POOR!
Russia has the Glonass system, Europe, Japan & China are developing their own systems

GPS_Scale

Relationship of distance on GPS screen to real world distance

A graphic scale showing actual distance
Usually based on screen width - check your manual

GPSbabel

The standard for converting between GPS formats

A FREE open source application that can convert to/from almost any GPS related format
Get GPSbabel here

GPSr

Global Positioning System Receiver

User portion of the Global Positioning System

GPSs

Global Positioning System Satellite - AKA "bird"

Satellite portion of the Global Positioning System
Weigh about 1,900 pounds each
Orbit ~ 12,000 feet @ 7,000 MPH
Has 4 atomic clocks onboard
Sends position & time accurate to 1 billionth of a second
Signal is designed to pass thru clouds, glass & plastic
Trees, standing water or snow and your body can anttenuate signals

GPX

GPX XML

.gpx file type extension
XML (eXtensible Markup Language e.g.like html) variant used for GPS information
Most newer GPS units and applications use this format
Elevation is stored in meters
Location is stored as latitude/longitude in degrees
Vendors can add their own "extensions"

gpx2img

Inexpensive tool to create Garmin transparent map overlays from tracklogs

I use it to provide my Garmin map overlays
Get gpx2img here

Icon

Generically means a symbol

Graphical representation of a waypoint on GPS screen
On some Lowrance units, a symbol for unnamed points that can't be navigated to

Interactive Map

A map that allows you to zoom, pan, or select map backgrounds or layers.

Google Earth and Google maps are examples of this
Many government entities allow you to select different layers of their GIS data
My site interactive maps allow selection of:
- m - Street Map Google
  
  s - Aerial Google Satellite
  
  h - Aerial Google Hybrid
  
  naip - Aerial USA
  
  t1 - Topo Google Terrain
  
  t2 - MyTopo USA-Canada
  
  t3 - Topo USGS USA
  
  t4 - Topo High USA
  
  t5 - Topo Canada
  
  t6 - Topo ESRI USA
  
  t7 - Topo ESRI World
  
  t8 - Topo OSM Cycle World
  
  osm - Open Street Map
  
  Earth
- Toggling these settings:
  
  My Location On/Off
  
  Directions
  
  Hill shading
  
  UTM - LatLng - Off
  
  Declination On/Off
  
  Data file On/Off
  
  Label On/Off
  
  Streetview On/Off
  
  Printing & ViewingTips
  
  "Full screen view"
  
  "Help" & "About"
  
  Button / Scroll interface

KML

Keyhole Markup Language

xml (eXtensible Markup Language) variant used by Google Earth
.kml file type extension
.kmz is file type extension for compressed form of this file

{aliases kmz|keyhole markup language}

Latitude

N/S position on globe in degrees - see Map Coordinate System

Zero at equator
+90 at N most point
-90 at S most point

Longitude

E/W position on globe in degrees - see Map Coordinate System

Zero at Grenwich England
+ to E of there, - to the W
180 on opposite side of globe

Map Clutter

Too much data on screen makes it harder to interpret

Some units have setting to control the amout of detail
Some units allow control of types of data shown
More detail is not always better!

Map Coordinate Systems

Model to specify locations on earth surface

Latitude Longitude height reference is most common
- References are the Equator & Prime Meridian
- Coordinates can be prefixed N|S & E|W
- Areas to west of Prime Meridian or below equator are negative numbers
- Can be described via different position formats: (Confluence Park)
  - Degrees (N 39 45.287 W 105 0.551)
  - Degrees, Minutes (N 39 45.287 W 105 0.551)
  - Degrees, Minutes, Seconds (N 39 45' 17.2" W 105 0' 33.1")
UTM - Universal Transverse Mercator
- Allows for easier distance calculations between coordinates (metric based)
- Comprised of zones:
  - Zone numbers designate 6 degree longitudinal strips
  - Zone characters designate 8 degree zones N & S from Equator
  - There a special zones for above 84 degrees N and below 80 degrees
- Measurements are refered to "Eastings & Northings
- Confluence Park: (13 S 0499213 4400541)
  - Zone 13 S
  - Easting 0449213
  - Northing 4400541
MGRS - Military Grid Reference System is an extension of UTM
GPS units will do transformations between coordinate systems and map datums they support

Map Datum

Model used to approximate shape of earth

There are hundreds of datums used around the world
WGS 84 is the most common datum used on GPS in US
WGS, latitude/longitude and meters is the standard for GPS data exchange (.gpx)
Differences using US datums could be hundreds of yards
GPS receivers do transformations to/from their supported datums

Map Orientation

GPS display setting that controls how you view map

North up - North is always at top of display
Track up - Direction you are heading is kept at top of display
Course up - Direction to next navigation point is at top (reverts to track up when not navigating)

Map Overlay

Layer of data on top of existing map

e.g. contour lines overlayed on aerial imagery
e.g. updated road layer on USGS quad map
e.g. my bicycle network on a Garmin or DeLorme GPS

Map Scale

Relationship of distance on "paper" map to real world distance

e.g. on a "24K" map, one inch on map = 24,000 inches on earth (1/24,000)
USGS "quad" (7.5' quadragnle) maps are 24K
24K in relation to a GPS map usually means it will show 20' contour lines
100K in relation to a GPS map usually means it will show 50' contour lines
Scale is usually shown on map legend

{aliases 24K|100K|quad}

Mounts

Hardware to allow you to hold your GPS on yourself or bike/car/atv etc

Usually model specific
However, most new Garmin handhelds use same mounting system
Vendors usually provide a variety of mounting options
DeLorme & Lowrance rely on Ram Mounts for their units
Ram has bases to mount on almost anything and cradles for devices from GPS to laptops!
I use them on my bikes

Open Street Map

OSM - Open Street Map

Open Source initiative that started in europe
Can load onto many Garmin units
- visit http://garmin.openstreetmap.nl/
- Select North America drop down
- Select State
- Select/deselect tiles as desired (Complete coverage of Colorado ~120MB)
- Click on "Question mark" symbol for information on download/install
Did I say FREE ?
Level of detail varies greatly depending on area!
I've included my trails into OSM - They may appear as cycleways, paths or tracks.
I've added hundreds of miles of canals/creeks/paths in front range area and aligned many hundreds of miles of highways etc.

{aliases OSM}

POI

Point Of Interest

Usage varies by unit
USer POIs are also known as waypoints
System POIs may show cities, businesses etc

Proximity Waypoints

Waypoints that you will be notified about when you get within a specified distance or time

Useful for avoiding hazards (e.g. under-water rocks, reefs, speed zones etc)

Raster Map

Map made from scanning a paper map

Typical examples are USGS Quad maps, satellite or aerial imagery
Unlike a Raster Map, it may not be visible at all zoom levels
At low zoom levels: the display is very crowded
At high zoom levels: the display gets "grainy"
Tends to require a lot of storage space
May slow operaion of GPS

Route

A series of points that a GPS can use to guide you to in order automatically

As you approach each turn, the GPS will notify you
When turn is reached, the unit guides you to next point
Routes can be reversed to guide your way back

{aliases routes}

Routing

The ability of a GPS to automatically generate a route to a given destination

AKA - turn by turn
Outdoor units provide on screen indication of approaching turns
Very few provide audio direction other than a beep
Many units will automatically recalculate after missed turns

Sensors

Garmin term for electronic compass & barometer/barometric altimeter

Topo

Topo - Short for "Topographic Map(s)

Generic term for a map that has contour lines (elevation)

{aliases Topographic}

Track Key

A two to five letter acronym for a trail

It is used as a prefix for trail waypoints
Used as tracklog name
Used as route name
Unique (at least at state level)
Color Coded - Matches track color

Tracklog

A series of points that a GPS automatically creates as you travel

AKA - "Bread Crumb" trail
Most GPSr allow you to navigate these after saving
Unit may create a route from saved tracklog data that may require an available route slot

{aliases Track|Tracks|Bread Crumb}

UTM

Universal Transverse Mercator - see Map Coordinate System

Allows for easier distance calculations from coordintes

{aliases Transverse Mercator}

Vector Map

Digital map that uses, lines, points & shapes

Map visible at all zoom levels
Lower memory requirements than a Raster Map
GPS can control level of detail as unit is zoomed in or out to reduce clutter
Some lines may be jagged, and road placements may not be exact

WAAS

Wide Area Augmentation System

Originally designed as back up airplane navigation/landing system
Uses Geo-synchronous satellites that send corrections to your GPS to account for atmospheric anomolies
Satellites 22,000 feet above equator over Atlantic & Pacific above equators
WAAS signals require southern view of sky
Master ground control station is in Colorado Springs

{aliases Wide Area Augmentation System}

Waypoint

A point that you manually set

Can be searched for and navigated to at a later time
Also refered to as Points Of Interest (POIs) on some devices

{aliases waypoints}