# Dead Reckoning Navigation System Basics | DR Navigation

This page describes **Dead Reckoning Navigation System basics**. It mentions how DR navigation system works.

**What is DR Navigation:**

Dead Reckoning Navigation System determines position of a vehicle based on its heading and
distance traveled even in the absence of satellite signal.

The DR navigation uses gyroscope (Gyro) to estimate heading. Later it uses heading along with distance traveled to determine position of a vehicle. The major challenge in this navigation type is when satellite signal will be lost for longer time due to long tunnel or other blockage of this type. In this condition error due to accumulated angle will become very large resulting into inaccurate position estimation.

## How DR Navigation Works

• Let us understand how DR navigation works. The idea is to determine location after some amount of time.
We will assume known position at start. The start position is taken at certain time.
Course is being noted as per true heading or compass heading.

• A gyroscope measures rotation rate of vehicle in degrees/second.

• Instantaneous heading of vehicle is calculated using integration of
rotation rate over time.

• Distance is determined based on speed and time of travel (some duration after which we would
like to determine the position).

• Based on initial known location (i.e. position at beginning of time of test) and
distance traveled as mentioned above, exact position of the vehicle can be
estimated.

The figure-1 depicts the distance calculation.
Let us assume coarse given is about 125 degree and position is known at start of time i.e. 8AM.
Let us determine position after 45 minutes of time.
45/60 gives us 0.75 decimal time.
We know speed of vehicle that is 10 knots/sec.
Now draw line parallel to coarse line (as shown in the circle) which represents 125 degree.
On this drawn line, we will get vehicle position using following formula.

Distance = speed x time duration

We get 7.5 knots as distance traveled on the coarse.

## Navigation Related Links

MEMS Gyroscope

DNS-Doppler Navigation System

INS-Inertial Navigation System

LORAN-Long Range Navigation System

RNAV-Random or Area Navigation System

TACAN-Tactical Air Navigation System

## What is Difference between

Difference between DME and TACAN

Difference between LDACS1 versus LDACS2

difference between FDM and OFDM

Difference between SC-FDMA and OFDM

Difference between SISO and MIMO

Difference between TDD and FDD

Difference between 802.11 standards viz.11-a,11-b,11-g and 11-n

OFDM vs OFDMA

CDMA vs GSM

Bluetooth vs zigbee

Fixed wimax vs mobile

wibro vs mobile wimax

Microcontroller vs microprocessor

FDM vs TDM

wimax vs lte