Marble/Manifesto

What Marble is all about

This page is a copy of

http://websvn.kde.org/trunk/KDE/kdeedu/marble/MANIFESTO.txt?revision=676415&view=markup

MARBLE - MANIFESTO

Principles and intentions of the Marble Project

v.0.3.2, April 12th, 2007

Virtual Globes have existed since decades already and have been subject of numerous papers in scientific research. Although many of them had been available for personal computers they only recently gained the awareness of public interest: Google Earth suddenly allowed people to spot their houses' roofs free of charge from high above and enabled them in combination with Google Maps to show their Google Search Queries referenced on a geographical map. Almost instantly Google Earth had become the "industry leader" among virtual globes that others had to measure up to [1].

Why Marble?

Today there exist numerous virtual globes and the market has embraced strong contenders such as Google Earth/Maps, MS Virtual Earth 3D and NASA WorldWind [2]. A new virtual globe project must be able to offer strong selling points and has got to focus on those without compromises. Otherwise it simply won't gain public relevance.

"Where?" is a pretty basic question that computer users have got to ask and answer quite often - no matter what they are working on. The free desktop has been advancing since years already. And while there's a pretty large amount of free software GIS ("Geographical Information System") applications available [3] they are mostly targeted at advanced users who deal with geo data during their daytime jobs or as a matter of enthusiasm. However, most people out there aren't cartographers and don't want to be. These people expect a simple and clean task-oriented interface that adheres to the map layout standards that decades of cartography have developed to improve ease of use of maps.

So for casual users there is still missing a fast, flexible, visually pleasing and easy to use map component. For developers, Marble offers a light-weight, fast, cross platform map component that can be used online as well as offline with meaningful results and that don't require proprietary webservices.

Marble is meant to become for "geo browsers" what KHTML/WebKit is for web browsers already.

From an average user's point of view a map component such as "Marble" should meet the following requirements:

1. FAST

   To allow instant access and usage as a widget the Marble Widget
   should start up instantly and be ready for use within 2-3
   seconds.  So "application" startup time should always be kept as
   low as possible.

   Technically this means that the Marble Widget needs to be heavily
   optimized for start up times and should have a minimal number of
   dependencies (as an increasing amount of libraries will slow down
   the application's launch).

   Most other virtual globes have startup times of 15-30 secs.
   That's just an eternity to wait for if you just want to look up
   something.

2. VISUALLY APPEALING

   The maps drawn by Marble Widget should adhere to visual
   cartographic standards and should look appealing.  Usually people
   prefer the 3D globe view as it looks more natural, mostly because
   of minimal distortion and because it looks more "advanced". It
   should be possible to easily print the maps and to embed them into
   documents without getting a pixel mess that is hard to decipher.

   Most other virtual globes don't offer good printing support and
   the graphical representation most of the time is just limited to
   satellite views that are often labeled pretty badly. Web based
   solutions (such as Google Maps) are quite static in their
   appearance and are limited in terms of possible modification.

3. EASE OF USE

   Another very important aspect is usability: The feature set should
   cover the use cases of the primary target user only.  3D flights
   are pretty exciting for users that want to be entertained.
   However most users don't need them, don't have the time to
   experiment with them or don't even discover that feature.  So
   focusing on the top-bottom view exclusively ("2.5D") makes sense
   for Marble.

   Maps should be easy to read.  In a lot of cases this will mean
   that the flat projection ("equirectangular projection" / "plate
   carrée") is more convenient (e.g. in a timezone chooser dialog).

   I personally consider Google Earth's interface too complex for
   most users we are aiming for.  Google Maps on the other hand seems
   too simple to me and also has a slight annoyance factor due to its
   web based nature.

4. MINIMAL HARDWARE/SOFTWARE REQUIREMENTS

   The Marble Widget should work at usable speed out of the box on
   all possible hardware the desktop environment is running on.  It
   should always show exactly the same output independent of the
   hardware.  During installation modifications to the system should
   stay as low as possible.

   This is an important point as people will simply neglect a
   solution if it's too painful to install or results in other
   unnecessary challenges during configuration.  Unfortunately many,
   if not most, computer systems out there don't offer decent 3D
   hardware acceleration for graphics.  So the solution we are aiming
   for should not depend on 3D hardware acceleration, although we
   certainly might want to offer solutions such as an OpenGL backend
   as an option.  Also the amount of software needed to install the
   map component should stay as low as possible (see 1.) ).

5. OFFLINE USAGE

   The Marble Widget should offer a minimal data set that is
   specifically edited and compiled for offline usage.  This is
   especially useful in countries where internet access is restricted
   or expensive.  Online usage should cover incremental downloading
   of texture tiles, vector data (e.g. OpenStreetMap) and wikipedia
   articles.
   Concerning offline geographical data Marble intends to deliver the 
   "biggest bang for the byte" and provide as much high quality 
   information per byte as possible.

   For all information that goes beyond map labels ("Marble Almanac")
   we have started cooperation with the Wikipedia Offline Reader
   Project.

6. FREE SOFTWARE & OPEN STANDARDS

   The Marble Widget is free software and should use a small set of
   open standards for communication with other applications at
   runtime and to save data to the storage medium.  The open KML file
   format[4] used by Google Earth is probably the most popular file
   format these days to geo reference data.  Through "feeding" KML
   streams to the map component, applications are offered a simple
   "programming" interface to control the map's appearance and
   behaviour.  All Information displayed on the map widget should be
   covered by free licenses using sources such as NASA or
   OpenStreetMap.

   Many other virtual globes are proprietary and are using commercial
   geo data that is considered "non-free" (as it isn't freely
   redistributable).

The Marble Universe

Apart from the Marble Widget (which is implemented using the Qt4.2 library only) there are other planned member components of the Marble universe:

1. Marble Desktop Globe

   KDE 4 application for KDE-EDU: This "reference" application is
   meant to show off much of Marble's full potential.  At the current
   point of time it's the next logical step as educational
   applications don't need to cover the data in full detail to be
   useful.  Once it reaches maturity the Marble backend could be
   moved into a more central place, e.g. kdelibs/base.

2. Marble Widget

   Can be used in different applications like KStars, KControl,
   DigiKam, KGeography, Kopete, Addressbook, Risk-Game, KWorldClock,
   Traceroute, Plasma Weather Applet, and so on. Depending on the use case
   it can have different appearances:
    - "normal" widget
    - selection dialog
    - developer mode

3. Marble Framework

   A framework of geo services for the desktop. This should cover a
   "position provider" backend like GPS, hostip.info, track turtle,
   and information services ( "Marble Almanac" ).

Torsten Rahn

References

[1] as an interesting read see the discussion section at

   http://www.earthslot.org/vgconference/VGconference_results.php

[2] for a nice introduction into virtual globes and a

   non-comprehensive list of them see the article at Wikipedia
   http://en.wikipedia.org/wiki/Virtual_Globe

[3] www.freegis.org provides a nice software overview on Free

   Geographic Information Systems

[4] KML 2.1 Reference available at:

   http://earth.google.com/kml/kml_tags_21.html