A datum is a mathematical model of the Earth. Map makers may use a different model to chart their maps, so position coordinates will differ from one datum to another. Lines of latitude and longitude on a map or chart are referenced to a specific map datum. Every chart has a map datum reference. The datum for the map you are using can be found in the legend of the map.

Geodetic datums define the size and shape of the earth and the origin and orientation of the coordinate systems used to map the earth. Please, request SymbianWare if you need some additional datums or projections. We may include new datums or projections in future versions. See similar questions...

The mathematics involved in map datum conversions are quite involved and will not be discussed here. Have a look here for software capable of transforming between different map datums. However, there is quite and easy way to convert from one map datum to another - available directly on your GPS ! Say for example that you would like to convert a waypoint from the CAPE map datum to the WGS84 map datum. See similar questions...

Flood Insurance Rate Maps (FIRMs) reference the elevation datum used to compute flood elevations. In completing elevation certificates, the same elevation datum as that shown on the FIRM must be used to compute lot and/or structure elevations, and to compute flood elevations that are not given on the FIRM. See similar questions...

The system is not using a vertical datum such as NAVD88 or NGVD29. It transmits vertical positional data in NAD83 ellipsoidal values. The user has to use additional means to derive the orthometric heights that are normally derived from vertical datums related to a geoid. These methods include local calibration to control points that already have NAVD88 values, application of a geoidal model or some other approach. See similar questions...

C-CAP data, provided on the Web, are distributed in Universal Transverse Mercator (UTM), North American Datum 1983 (NAD83), meters. The reason for the use of a Mercator-based projection is that raster data are not well represented in Geographic Latitude/Longitude (GLL) projection. GLL is a non-Cartesian coordinate system, meaning that the pixel size will change over space, becoming more extreme as you approach the poles. See similar questions...

Use the zoom bar and arrows on the top left hand side of the map to zoom in and out and north, south, east or west. You can also search by postcode or landmark type using the search field. You can also grab and drag the map around to navigate by using your mouse. Postcode searches will land you in the middle of that postcode area. You can then click on any icon that interests you to read a full description and adopt it. See similar questions...

A Flood Insurance Rate Map (FIRM) references the elevation datum used to compute flood elevations. In completing elevation certificates, the same elevation datum as that shown on the FIRM must be used to compute lot and/or structure elevations, and to compute flood elevations that are not given on the FIRM. See similar questions...

To export a projected raster project to a vector file in Didger 2.05, select all the digitized objects and go to File | Export. In the Export dialog box, check the check box in the lower left next to Selected Objects Only and export as normal. Exporting to a DAT file was a problem in earlier versions of Didger 2 (versions 2.00 and 2.01) when calibrated coordinates increase from right to left on the X axis, increase downwards on the Y axis, or one of the axes was logarithmic in scale. See similar questions...

A map has a notion of comparison, since one of its template parameters is a comparison function. However, operator< for maps uses the elements' operator< rather than that comparison function. This appears odd, but it is deliberate and we believe that it is correct. the most trivial level, this isn't a bug in our implementation because it's what's mandated by the C++ standard. (The behavior of operator< is described in Table 65, in section 23.1. See similar questions...

Datum is like frame of reference. Each point at earth surface is defined as combination of latitude, longitude and elevation. But all the three values depend on origing of coordinates, direction of axes, and accuracy of measured Earth radius and polar flattening. Different datums are used in different countries. As a result, coordinates of the same point may differ in two datums. For instance, Russian maps are based on "Pulkovo-1942" datum. The one used in GPS is WGS84. See similar questions...

OmniSTAR VBS in North America is on the NAD83 datum and ITRF00 in all other OmniSTAR world areas. OmniSTAR HP and XP are in ITRF00, worldwide. Some GPS receivers have the capability to convert and output the Position Data in various datums. This is a choice made by Receiver Manufacturers. Check for this option and your receiver settings to be sure. The reason for keeping the VBS in NAD83 in North America, is somewhat complex. See similar questions...

The first is something called a "datum". In simple terms, this is the "model" used to represent the shape of the earth. This is necessary, because the earth is not really round. WGS-84 is an example of a map datum. Other common datums in use are NAD27 and NAD83. We use WGS-84 here, because the Global Positioning System itself uses it. By the way, your GPS probably also defaults to this datum, so you shouldn't need to change it. See similar questions...

Chart Datum is the plane below which all depths are published on a navigational chart. It is also the plane to which all tidal heights are referred, so by adding the tidal height to the charted depth, the true depth of water is determined. By international agreement Chart Datum is defined as a level so low that the tide will not frequently fall below it. In the United Kingdom, this level is normally approximately the level of Lowest Astronomical Tide. See similar questions...

First create the user in NT that you'll want to have mapped through Authentix. Once you've done this, edit your NTFS security properties for the directory or directories you want protected. If you add a group to the NTFS permissions, make sure your user is in that group! In Authentix, click Access from the menu. Then add the directory you want to protect and map to the NT account. See similar questions...

The Future Land Use Map is a component of the CPP that identifies the proposed general distribution, location, and extent of residential, commercial, industrial, agricultural, conservation, institutional, and other land uses within the time horizon of the CPP, the year 2020. The Future Land Use Map reflects the goals, objectives, and policies of the CPP relative to land use planning. See similar questions...