Download Collecting and Recording Field Data: Spatial Position, Tools, and Errors and more Quizzes Geography in PDF only on Docsity! TERM 1 What is important to collect for field data (2) DEFINITION 1 spatial position (where)attribute (what) TERM 2 How to record spatial position DEFINITION 2 based on distance and direction TERM 3 Tools to measure distance (5) DEFINITION 3 tapingstadia opticsultrasonic distanceelectronic distance (laserGPS TERM 4 Tools to measure angle (4) DEFINITION 4 compassleveltransittotal station TERM 5 Taping (2) DEFINITION 5 observing the straight-line distance between a starting point and an ending point along each leg of a traverse Sources of error: tape alignment compensation of tape length TERM 6 Ultrasound distance DEFINITION 6 sound waves at a frequency above the limits of human hearing Distance m = 1/2 travel timesec * 340 m/sec TERM 7 Electronic distance (laser) DEFINITION 7 laser: electromagnetic energy travels at 3 x 10^8m/sec Distance m = 1/2 travel timesec * 3 x 10^8 m/sec TERM 8 Total station DEFINITION 8 measures horizontal/vertical angles and distance TERM 9 What is a prizm used for DEFINITION 9 used for reflecting laser light back to the total station TERM 10 What are the 2 angles that are used in the field DEFINITION 10 horizontalvertical TERM 21 What is a scanned map (3) DEFINITION 21 it is merely an image, no digitized features(roads) and the coordinates are relative to the printed medium TERM 22 How many common points must you identify DEFINITION 22 at least 4 common locations TERM 23 Image scanning in the conversion process (3) DEFINITION 23 Modern methods of recording the spatial location of features on maps or aerial photographs use the conversion process. Scanning a map or aerial photograph is the first step in the conversion process. Once the map/photograph is converted into a graphic image it is then rectified to a ground coordinate system and then the spatial position of features are recorded. TERM 24 Scanning/rectification considerations (4) DEFINITION 24 Decide on Scanning Resolution (Spatial and Color) Should be able to see: Control points Features of interest Decide on Output Data Structure Must be compatible with GIS scan imagerectification process TERM 25 Scanning characteristics: size (2) DEFINITION 25 topographic map 23x19 aerial photograph 9x9 TERM 26 Detail needed (2) DEFINITION 26 Spatial Resolution (measured in dots per inch) e.g. 100 dots per inch, 400 dots per inch Color Resolution or Depth (8, 24, or 36-bit) 8-bit color only provides 256 shades of B/W 24-bit color provides 16.8 million unique colors TERM 27 Image space DEFINITION 27 scanned map or photo TERM 28 Real world space DEFINITION 28 ground surface on map projection TERM 29 Georeferencing DEFINITION 29 the process of relating coordinates in one space to another space TERM 30 Control points (2) DEFINITION 30 one-to-one relation between pointsPoints in map projection may come from a map or surveyed in field TERM 31 Link DEFINITION 31 one location in each corresponding space TERM 32 Least square regression model (2) DEFINITION 32 Establishes one-to-one relation for all locations in image space (xi and yi) and real-world space (x,i and y,i).x = a + bx,i + cy,i y = d + ex,i + fy,i TERM 33 Steps in geometric registration of a map (6) DEFINITION 33 Scan map/photo Digitize corresponding control points on scanned image and map projection (use x-y coordinates) Select best least squares model (e.g., 1st order polynomial) Evaluate Root Mean Squared Error (RMS) statisticIf RMS is unacceptable evaluate control points Register image TERM 34 Translation DEFINITION 34 shifting the image so that two points coincideone control point solves translation TERM 35 Rotation DEFINITION 35 two control points solves both translation and rotation
