GISP Study Questions and Answers Rated A+

GISP Study Questions and Answers Rated A+ Georeferencing 101- associating a map or image with spatial location control points 101- points come in pairs that match the spatial location with a point on an unreferenced image or map Spatial Reference Systems (SRS) 101- coordinate based local, regional, or global system used to location geographical entities (aka Coordinate Reference System (CRS)) Coordinate Reference System (CRS) 101- coordinate based local, regional, or global system used to location geographical entities (aka Spatial Reference Systems (SRS)) International Terrestrial Reference System (ITRS) 101- a three-dimensional coordinate system with a well-defined origin (the center of mass of the Earth) and three orthogonal coordinate axes (X,Y,Z) Map projection 101- transforming coordinated from a curved surface (Earth) to a flat map Horizontal datum 101- model of the earth as a spheroid (2 components, reference ellipsoid and a set of survey points both the shape of the spheroid and its position relative to the earth) Vertical Datum 101- reference point for measuring elevations NAVD88 101- Gravity based geodetic datum in North America WGS 84 (World Geodetic System) 101- reference coordinate system used by the Global Positioning System (GPS) SRID integer 101- Spatial reference system id numbers, including EPSG codes defined by the International Association of Oil and Gas Producers types of distortion 101- Distance, Direction, Shape, Area (sometimes bearing and scale) Mercator Projection- distortions 101- preserves shape and direction, area gets distorted Mercator Projection 101- projecting the Earth onto a cylinder tangent to a meridian Azimuthal Projection- distortions 101- distance from center is true, other properties distort with distance Azimuthal Projection 101- planar or tangent (meaning they are formed when a flat piece of paper is placed on top of the globe and a light source projects the surrounding areas on to a map.) Either the North Pole or the South pole is orientated at the center of the map, giving the viewer an impression of looking up or down at Earth. Cylindrical Projection- distortions 101- preserve area and shape, distance gets distorted, especially on upper and lower regions of the map Cylindrical Projection 101- 2 types Tangent (1 intersect) and Secant (2 intersects) Straight meridians and parallels meridians are equally spaced while parallels are not Conical Projection- distortions 101- preserves direction and area in limited areas, distorts distance and scale except along standard parallels Conic Projections 101- mapped to equally spaced lines by projecting a spherical surface onto a cone Choosing a Projection- Low LATITUDE, (near Equator) 101- use conical projection Choosing a Projection- High LATITUDE, Polar Regions 101- use azimuthal planar projections Choosing a Projection- EXTENT, broad East-West (e.g. USA) 101- use conical projection Choosing a Projection- EXTENT, broad North-South