# GPS sky

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## Presentation Description

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By: ahmedsalim (114 month(s) ago)

thank u

By: unleash.thunder (117 month(s) ago)

lodu.....

## Presentation Transcript

### GPS SKY :

GPS SKY What is the Sky Doing Today?

Objective

### Slide 3:

Summary of Topics - Importance of Planning - Review how GPS Calculates Positions - Check Out The Sky - Planning Ahead

### Slide 4:

Planning the GPS Day Recreational GPS is very forgiving It’s for fun! Not for worrying about PDOP,SNR,Mask Angle,blah blah… Designed to Work inside your Pocket! Still important - as will be demonstrated

### Slide 5:

Tracking a GPS Satellite Vehicle (SV) One of 29 12,000 miles up 6000 mph JTRACK http://liftoff.msfc.nasa.gov /RealTime/JTrack/3D/JTrack3D.html

### How to Calculate a Position :

How to Calculate a Position Measure the Distance to the Satellites Review

### How to Calculate Distance :

How to Calculate Distance Speed of Light x Travel Time Distance Time signal left satellite Current time Review

### Minimum # of Satellites Required :

Minimum # of Satellites Required 4 Unknowns Require 4 Satellites time ...……………… (1) satellite latitude ……………. (1) satellite longitude .…………. (1) satellite elevation …..…….… (1) satellite 4 Satellites = 3D Good 3 Satellites = 2D BAD A Garmin will allow 2D positioning! Watch Out!

### PDOPPosition Dilution of Precision :

- Want tetrahedron as large as possible - Want index as low as possible PDOPPosition Dilution of Precision

### Garmins View of Mapping :

Garmins View of Mapping Typical Mapping Grade GPS Settings - PDOP = 99 - SNR = 2 - Mask Angle = 5 º PDOP = 6 SNR = 6 Mask Angle = 15º Garmin Says... GO FOR IT!

### PDOP / DOPPosition Dilution of Precision :

Rules of Thumb PDOP of 6 or Less - Good DOP of 3 or Less - Good PDOP / DOPPosition Dilution of Precision Garmin only Shows DOP That’s 1/2 of PDOP Garmin III Plus Screen

### Slide 12:

Tools for Predicting - See PDF on How To: CD</software/TrimblePlanSoftware Almanac File: Software: From CD </software/TrimblePlanSoftware or http://www.trimble.com/planningsoftware_ts.asp

### PDOP and Visibility Graphs :

PDOP and Visibility Graphs Instructor Runs Trimble Planning Software for Today

### PDOP and Visibility Graphs :

PDOP and Visibility Graphs