In order that a GPS receiver understood point
coordinates sent to him, and vice versa, it is necessary to tell
software what is the referential placed on the map (Scale tab).
To achieve this, origin coordinates and axis length must be
correspond to the map indications in a absolute way (geo-referencing).
Scale placement in this context is mentioned in this document
under the term of Calibration.
Note that a map calibration can be changed at any time without any information loss on the current route.
eMapZone accept several system for the calibration :
eMapZone works with this system to memorise and save the coordinates of points, because they stand directly for meters. The UTM system (Universal Transverse Mercator) is a world-wide standard for geo-referencing, most of the GPS accept it, and, although its grid has one kilometre steps, even country used to statute (miles/feet) system use it. The UPS system is the UTM equivalent near the poles.
The earth is divided into 60 zones, the first one around the Bering strait :
For west to east : at the top, the sixty UTM zones ; at the bottom, the longitude on degree from Greenwich meridian.
From North to south : at left, the latitude in degree ; right, UTM letters (unused in eMapZone)
Thanks to http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys.html
This is a corner of a map with a UTM grid :
|If the scale origin is place on the grid cross (there
is little chance to set it here because X and Y axis will
not fit, but this is just an example), map origin fields
will be set with :
x = 680000
If you do not known the UTM zone, a technique is to enter at origin a value in dd°mm'ss'' (most of the maps mention at least one longitude in degree from the Greenwich international meridian), for instance -70°17'00'', and then to change to the UTM grid : the zone is automatically computed. Another technique is to read what's given from a GPS receiver if it is physically located on the map area.
This system is used with French maps from Institut Géographique National (IGN). Old IGN maps do not contain a GPS grid, so the Lambert system can be used for calibration. These maps are marked out with little crosses (croix = some "+"), evenly spaced at each kilometre. They are Lambert zone I II III or IV trailers. When this system is used, coordinates are shown, memorised and saved directly in this system.
IGN map 1/25000 Top25 without GPS grid
|If the scale origin is set on the "+" just
under the Castelas word, these values must be
x = 864000
Lambert zone is automatically detected = III
Some maps only contain degree references. In this case, the scale origin must be set on a meridian/parallel intersection and grid set to dd°mm'ss.s''. When this grid is selected, axis length must be set in this same format. Note that eMapZone always memorise and save UTM data for its internal management and computation. Note also that the software suppose that meridians and parallels fit on a straight grid. On the longitude axis, the reference is the Greenwich meridian. For west longitudes, enter a negative sign "-" before the degree value. The map datum should be indicated on the map itself.
The Datum stands for values needed for projecting computation and referencing of coordinates on the globe (ellipsoid, Tx Ty Tz...). In general, the WGS84 datum is a standard because this is the system that GPS satellites use. But it is preferable to check map information where the used datum should be indicated.
The Grid... button at the bottom of the scale panel gives access to a window allowing to move the scale with a result viewing on the whole map. It is possible to zoom/unzoom during its use. When this window is visible, a red grid corresponding with the used scale is drawn on the map, and the different buttons can change it :
Fine tuning : check this box in order that button actions are more precise on the desired tuning
Origin, four direction buttons : change the grid offset in the up-down and left-right buttons (relatively to the screen)
Act on : choose on which axis the four next buttons will act
Size -+ : change the axis length in pixels (terrain length is not changed!)
Angle -+ : axis rotation (positive way = trigonometric way)
Start setting the scale in a standard way : origin, X, Y... zoom while clicking for precision
Then use the Grid tool. Most of the time, origin position is correct, go directly to the axis size and orientation tunning.
Axis size : along X then Y, grid must be perfectly overlapped with the one of the map. Far from the origin, changes will become more and more sensitive.
Axis angle : far from the origin, try to make the line the right direction
Beware, the scanned map can present deformation, its flatness can be altered, it is sometimes difficult to get a homogeneous result. Try to do the best near the route itself. Results with a GPS receiver are most of the time quite precise.
In the Options tab, it is possible to set what are the GPS system to use when creating a new document. At the first use of the software, the UTM zone is computed from the current time zone. This computation is an approximation because there are 24 time zones and 60 UTM zones. The correct value should be set.
The GPS dialog box is accessible from the GPS, Transfer data menu. The window contains tabs on the left for settings and actions, a list for transfer result, a state panel at the bottom and arrows for data stream changing colour during communication. This window is sizeable.
When window is shown, eMapZone checks that the map calibration has a correct GPS reference. Otherwise, a warning is shown on the state panel.
In order to check that the device is correctly connected and recognised by the software, settings must be specified :
The LOG is the record of successive positions of the receiver in a continuous way, also called Track. With eMapZone it is possible to get this record back from the GPS in to see the trip, on the map, where the receiver was. With a Garmin receiver, it is possible to send a LOG to the GPS in order to follow it exactly as it was drawn on the map with eMapZone.
Note that the LOG is made of points containing less information than Waypoints (see next tab), so it will be necessary to proceed in two steps to send or get real waypoints.
This panel allows to get the LOG from the GPS :
Click the Read LOG button. Point coordinates are shown in the list during the reception
The Validate and Close button is activated at the end of the transfer. It will close the window and show the LOG on the current map.
Leave the Remove points out of map checked : at LOG validation, points without the map area will be eliminated. If the calibration is not correct, no point will be added.
Some GPS give altitude of each point, some do not.
During validation, the current route document is deleted : it is possible to cancel with the Edit; Cancel menu.
This transfer is only possible with Garmin GPS (its a Magellan limitation). The Send Log button :
All the points from the eMapZone route are sent to the GPS. Remember to clear the LOG in the GPS itself first.
GPS devices are limited for the total number of points (1024 for a Garmin 12) : check this limit.
Check the map calibration ; if wrong, the LOG will be sent to the GPS but will physically refer to a wrong place in the world.
This panel allow to get Waypoints from the GPS touching the current eMapZone route. That's why a route document must be present in the software (otherwise the Read Waypoints button is not active).
Click the Read Waypoints button. The list shows the waypoints read from the GPS.
If at least one waypoint was read, the Validate & Close button is activated at the end of the transfer. Click on it : the window is closed and the waypoints close to the current route are inserted in it.
Typically, this transfer should be done immediately after the LOG transfer to get Waypoint entered during GPS usage on the recorded itinerary.
With this panel, it is possible to :
Send Waypoints and make a route with them in the GPS. The Waypoints are sent and linked as a route (as the GPS specify a route), with an index which can be entered. Document name is also sent.
Send Waypoints alone. Typically, this should be done immediatly after having sent the LOG to the GPS, in order to see its LOG marked out with Waypoints given by eMapZone.
Sent waypoints can be :
Only those having a name (most used option)
Only those having a name or with a known altitude (not interpolated) ; in this case, the name of the Waypoint is generated from its altitude and its index inside the route.
All the points.
Point names should not be duplicated otherwise the last sent will replace previous with same name.
Point names are modified in order that GPS can accept them. Accents, spaces, special characters are eliminated and the total length is truncated (depending on the GPS model)
In the comment zone proposed by the GPS is placed the complete name of the name followed by its altitude. If the points contains a note (annotation), it is used instead.
Some GPS devices limit the total number of waypoints for a route (30 for the Garmin 12), that's why route usage is not so interesting compared to the LOG.
Waypoints will always have the default graphical symbol : this will offer a practical way to remove them from the GPS (delete "by symbol").
Prepare a itinerary with eMapZone and be guided by your GPS on the field. Follow these steps :
Another possibility is the send a route to the GPS ; this option is less precise because the route is made of named waypoints, without intermediate points, and most of the time the total number is limited. Interest : the GPS gives you the directions and you can stored many routes. But note that you can choose to "track-back" the active log : a route is automatically generated.
Another interesting usage : record moving on the field and see them later at home on you screen. Magic !
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