ESS 375 Exam Review Flashcards
ARC Map
Application for making maps and analyzing data
ARC Catalog
GIS application for data management.
ARC Toolbox
Provides a reference to the toolboxes to facilitate user interface in ArcGIS for accessing and organizing a collection of geoprocessing tools, models, and scripts.
This Is How LORAN Works
Based on measuring the time difference between the receipt of signals from a pair of radio transmitters
Significance Of LORAN
Helps vessels to determine their position at sea by using shore-based radio transmitters and onboard receivers.
USNO NAVSTAR Stands For
Navigation Satellite Timing & Ranging) US Navigation system
GLONASS
GLONASS was developed by the Soviet Union as an experimental military communications system during the 1970s. When the Cold War ended, the Soviet Union recognised that GLONASS had commercial applications through the system’s ability to transmit weather broadcasts, communications, navigation and reconnaissance data.
GALILEO Stands For
Is currently the worlds most precise satellite navigation system, serving more than 3.5 billion users around the world.
BEIDOU IS
The BeiDou Navigation Satellite System (BDS) has been independently constructed and operated by China with an eye on the needs of the country’s national security and economic and social development. As a temporal-spatial infrastructure of national significance, the BDS provides all-time, all-weather and high-accuracy positioning, navigation and timing services to global users.
IRNSS Is
Indian Regional Navigation Satellite System which is an independent satellite system that is designed provide accurate position information services to users in India as well as the region extending up to 1500km from its boundary.
QZS Is
- Quasi Zenith Satellite Orbit
- Satellite positioning systems use satellite signals to calculate position information. One famous example is the American Global Positioning System (GPS); the QZSS is sometimes called the “Japanese GPS.”
Minimum Number Of Satellites Needed For Worldwide Coverage
You need 24 Satellites
Ephemerides
Gives the trajectory of naturally occurring astronomical
objects as well as artificial satellites in the sky the position & velocity over time.
Pseudorandom Code
This is an identification or ID code that
identifies which satellite is transmitting the information
This Is The Information Carried In The Almanac
Status and low-resolution orbital
information for every satellite
This Is How High Satellites Are
20,000 km
This Is Why Atomic Clocks Are Important
The atomic clocks had better frequency stability than
earlier clocks, which greatly improved the prediction of
spacecraft orbits (ephemerides) and would eventually
extend the time required between control segment
updates to GPS satellites.
This Is How Atomic Clocks Work
Every satellite needs one in order to get the time variable required for calculating position. They operate by exciting rubidium and cesium particles to create pulsating waves. The pulse rate is known and constant and allows time to be tracked through pulsating frequencies.
GPS Errors Are
Errors in the system that do not give you the correct information.
This Is What GPS Errors Cause
- Multipath Error = When GPS signals bounce off other
objects prior to receiver antenna. - User Equivalent Range Errors
This Is The Significance Of Ionspheric Delay
As GPS signals pass through the upper atmosphere signals are delayed and deflected.
- The ionosphere density varies →signals are delayed more in some places than others.
- The delay also depends on how close the satellite is to being overhead (where distance that the signal travels through the ionosphere is least).
This Is The Significance Of Atmospheric Delay
The lower atmosphere delays GPS signals, adding slightly to the calculated distances between satellites and receivers.
Signals from satellites close to the horizon are delayed the most, since they pass through the most atmosphere.
This Is What UTC Stands For
Coordinated Universal Time
DARPA Stands For
Defense Advance Research Project Agency