Notes

SOME SOURCES OF DATA FOR GIS
1. MAPS
2. CENSUS AND SURVEY DATA - MAY BE SPATIAL IN CHARACTER IF EACH ITEM HAS A SPATIAL REFERENCE, USUALLY A TABULATE FORMAT. EX. POPULATION CENSUS, EMPLOYMENT DATA, AGRICULTURAL CENUS DATA AND MARKETING DATA.
3. AERIAL PHOTOGRAPHS- FIRST METHOD OF REMOTE SENSING, A SNAPSHOT OF THE EARTH OF A PARTICULAR INSTANT IN TIME, SNAPSHOT, MAYBE USED AS A BACKGROUND OR BASE MAP, PROIDE SPATIAL CONTEXT, VERSATILE, RELATIVELY INEXPENSIVE AND DETAILED SOURCE, DISADVANTAGE IS NOT SPATIALLY REFERENCED USING OTHER DATA ( EX. MAPS, GPS DATA, LAND SURVEY DATA)
IMPORTANT CHARACTERISTICS OF AERIAL PHOTOS FOR GIS (CURRAN 1989)
-WIDE AVAILABILITY
-LOW COST COMPARED WITH OTHER REMOTELY SENSED IMAGES
-WIDE AREA VIEWS
-TIME FREEZING ABILITY
-HIGH SPECTRAL AD SPATIAL RESOLUTION
-3D PERSPECTIVE
4. SATELLITE IMAGES- COLLECTED BY SENSORS ON BOARD A SATELLITE WHICH ARE THEN RELAYED TO GROUND STATIONS, CAN BE USED TO DETECT FEATURES NOT READILY APPARENT TO THE NAKED EYE (SEDIMENTATION, MOISTURE CONTENT), PROCESSING IS NEEDED FOR DATA REDUCTION, GEOREFERENCING, ENHANCING
ADVANATGE:
-EASY TO TRANSFER
-SPECIFIC FEATURES CAN BE HIGHLIGHTED
-REPEATED COVERAGE OF THE EARTH- IMPORTANT TEMPORAL ANALYSIS AND CONTINUOUS MONITORING
-LARGE COVERAGE AREA- USEFUL FOR REGIONAL OR NATIONAL MAPPING APPLICATIONS
-LOW COST COMPARED WITH OTHER DATA SOURCES
-ABILITY TO ACQUIRE CURRENT/TIMELY IMAGES
-ACCURATE AND COMPLETE
-UNIFORM STANDARDS ACROSS AREAS
5. GROUND/LAND SURVEY DATA- USING TAPES, TRANSITS, THEODOLITES, AND TOTAL STATION, USED TO COLLECT FIELD DATA SUCH AS COORDINATES, ELEVATIONS, AND DISTANCES, AND DATA COLLECTED ARE IN ANALOG FORMAT(WRITTEN DOWN IN PAPER) WHICH STILL NEED TO BE TRANSFORMED TO DIGITAL FORMAT FOR USE IN GIS.
6. GPS DATA- RELATIVELY NEW TECHNIQUE OF FIELD DATA COLLECTION, RADIO WAVES/SIGNALS FROM GPS SATELLITES, ORIGINALLY DESIGNED FOR REAL TIME NAVIGATION, CAN STORE COLLECTED COORDINATES AND ASSOCIATED ATTRIBUTE INFORMATION, ACCURACY RANGES FROM 100 METERS TO A FEW CENTIMETERS.

CATEGORIES OF GEOGRAPHIC DATA ACQUISITION
-PRIMARY- COLLECT THROUGH FIRST HAND OBSERVATION
-SECONDARY- DATA COLLECTED BY ANOTHER INDIVIDUAL OR OTHER MEANS.