FAQ of Lux Navalis

What is a vector chart?
Vector charts are stored as drawing elements (instead of pixels). Each ground, safety device or area is saved as positional data. The chart is always redrawn according to this data at the required accuracy. Vector charts differ from scanned charts by the way they are redrawn. They are not just enlarged or reduced images of the chart. Vector charts can be edited during redrawing. Some elements can be left undrawn (different features on different layers).

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From whose data are the vector charts of Lux Navalis made of?.

The charts in Lux Navalis are made of the same Fingis-data as the official charts. All the details in Lux Navalis are drawn exactly at the same places as in the official charts. Drawing technique is somewhat different from that in the official charts (e.g. lines with flames and cables).

Can we replace the official charts with Lux Navalis?
No. The only official charts are those publishec by the Maritime Authorities and printed on paper or the authorized ECDIS-systems with ENC-material. No matter how well a company tries to make the programs a fact is that computer programs always contain bugs. If the official paper chart is different from the Lux Navalis chart always believe the paper chart.

Can we have "blue charts" in Lux Navalis?

The INT-charts published in 2003 by the Maritime Authorities of Finland differ from those in Lux Navalis in:

The co´ordiante system in the INT-charts is based on the wgs-84 system. This causes the longitude- and latitude-lines to be in different places. The difference has no effect in the usability of the program.

Part of the place-names is changed - the difference is insignificant.

Some chart symbols have been changed. The change does not reduce the readibility of the chart.

Colouring is blue. Lux Navalis has used this colouring mode since year 2000.

Click on the image to see the chart enlarged.
All the grounds, safety devices, depth curves and other chart markings are in the same places!

Automatic Routing

The automatic routing procedure takes into account the indicated depth of the vessel. It does not compose a route in too shallow lanes. Lux Navalis moves the route a predetermined distance to the right of the lane-line (default 18m). Bridge and power line hights as well as the width of the lane is left for responsibility of the skipper. Sometimes a route, composed on the chart, goes ashore in reality. Be aware and be critical when to use autopilot!

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Gps-tarkkuus?
GPS is in good conditions a relatively accurate positioning device. However, the position given by a gps may be several hundreds of meters wrong. This may be due to:

The US-army may cause random disturbance in the positioning. The disturbance was stopped on 1.5.2000.
Inaccuracy between instruments from different manufacturers may be even two-fold compared to those indicated by the makers. This is based to the fact that the direction of inaccuracy is not known.
Bad satellite configuration or shielded satellites cause inaccuracy.

The best instruments can give the position at an accuracy of les than one meter when using differential correction. Differential correction device is a good add to the gps-navigator. In some situations a differential receiver may weaken the accracy of the gps. Lux Navalis has a residual-value control of the positioning of certain gps-devices.

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Why should we not autopilot-steer the same route in opposite directions?
On the seas as well as on land it is a rule to go on the right side of the passway. Steering on the wrong side or even at the center of the lane can be dangerous.

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Why is it not possible to change waypoints while the GPS is active?
It is too dangerous because the attention would be moved away towards the computer instead of navigation and watch-keeping.

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Why is it impossible to makeup a route from the passed track?
The inaccuracy of the positioning device and deleted track points would cause short-cuts over shallow waters or over grounds.

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How many routes, waypoints, tracks and notes can Lux Navalis handle?
The amount of data is restricted only by the capacity of the hard disk of the computer. In practise the capacity is unlimited. One route can not, however, have more than 999 waypoints because many autopilots do not accept numbers higher than 999. This limitation is not set by Lux Navalis.

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Is it possible to upload the Lux Navalis -routes into the GPS?
Yes and no. Lux Navalis saves a route plan into a file from which the data can be transferred into the format of different gps-devices. This can be done manually or by using a small program or even with a word processing program. We can colect such small programs into the www-pages of Lux Navalis if necessary. Lux Navalis can save the routes as WPL- or RTE-messages. Some gps-devices know how to download the routes from these files.

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Are the charts in Lux Navalis boundaryless?
Yes and no. The charts based on the national KKJ-co´ordinate system contain boundaries of discontinuity. The fundamental maps are in the KKJ-system. The discontinuity boundaries are on longitudes 19.30, 22.30, 25.30, 28.30 and 31.30.

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Are the grounds in Lux Navalis in the same places as in the official charts?
Yes, they are. The Lux Navalis -charts are produced from the same data as the official charts. Grouds and other objects are in the same and equally accurate places as in the official charts. Originally the grounds and other objects were drawn on the charts based on observations by naked eye. Today the positions of the objects are measured and the numerical values are used to draw them on the charts. Quite many objects are, unfortunately, still drawn on the charts according to their positions which were previously drawn on the old charts and digitised from them.

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Does computerized navigation weaken the traditional navigation skills?
On the contrary! If the user of such a navigation program has any interest to learn the traditional navigation skills, a good navigation program can be a tireless and accurate resource of comparison for his own observations and decisions. REMINDER: Be aware that the navigation program is only an aid for navigation.

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The accuracy of Route Planning
A route must be planned on the chart so that it can safely be navigated. Things affecting on the safety are the accuracy and clearness of the chart. With the aid of Lux Navalis routes can be planned even in the densest archipelago where the accuracy of the old raster charts is not enough. The accuracy of charts digitized from old paper raster-charts by scanning. Safetymargins should be kept large enough if these charts are used (e.g. in the coarsest raster charts of Lux Navalis the margins should be kapt in several kilometers!). It is a good practise to check and recheck the route plannings especially if they are followed with auto pilot - in narrow places the route may be ashore.

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Night views
Man sees with the two different types of light-sensitive cells in the eye.
In night-time it is best to split the actions to steering and navigation. The helmsman should never even glimse on the computer screen but only steer according to the instructions given by the navigator.

A flock of birds stationary in an open sea
A flock of birds stationary in an open sea may indicate the presence of a shallow area. Be aware!

Why is the ship shown 170m in the wrong place on the chart?
The datums (co´ordinate systems) of the gps-device and the chart are in conflict. Correct the error either within Lux Navalis or in the gps-device.

What material must be purchased for the 3D-display on land?

For the 3D-display on land you have to buy the NLS 25m height-data. This data is delivered only with the basic maps. It must be purchased from Hannu Säles Oy, Ltd.

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http://www.hannusales.fi This page was translated into English by Jouko Mäki on 2003 12 14 and modified on 23.05.2004

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