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0001 0002 MARBLE - MANIFESTO 0003 0004 Principles and intentions of the Marble Project 0005 0006 0007 v.0.3.2, April 12th, 2007 0008 0009 0010 Virtual Globes have existed since decades already and have been 0011 subject of numerous papers in scientific research. Although many of 0012 them had been available for personal computers they only recently 0013 gained the awareness of public interest: Google Earth suddenly allowed 0014 people to spot their houses' roofs free of charge from high above and 0015 enabled them in combination with Google Maps to show their Google 0016 Search Queries referenced on a geographical map. Almost instantly 0017 Google Earth had become the "industry leader" among virtual globes 0018 that others had to measure up to . 0019 0020 0021 Why Marble? 0022 =========== 0023 0024 Today there exist numerous virtual globes and the market has embraced 0025 strong contenders such as Google Earth/Maps, MS Virtual Earth 3D and 0026 NASA WorldWind . A new virtual globe project must be able to offer 0027 strong selling points and has got to focus on those without 0028 compromises. Otherwise it simply won't gain public relevance. 0029 0030 "Where?" is a pretty basic question that computer users have got to 0031 ask and answer quite often - no matter what they are working on. The 0032 free desktop has been advancing since years already. And while 0033 there's a pretty large amount of free software GIS ("Geographical 0034 Information System") applications available  they are mostly 0035 targeted at advanced users who deal with geo data during their daytime 0036 jobs or as a matter of enthusiasm. However, most people out there 0037 aren't cartographers and don't want to be. These people expect a 0038 simple and clean task-oriented interface that adheres to the map 0039 layout standards that decades of cartography have developed to improve 0040 ease of use of maps. 0041 0042 So for casual users there is still missing a fast, flexible, visually 0043 pleasing and easy to use map component. For developers, Marble offers 0044 a light-weight, fast, cross platform map component that can be used 0045 online as well as offline with meaningful results and that don't 0046 require proprietary webservices. 0047 0048 Marble is meant to become for "geo browsers" what KHTML/WebKit is for 0049 web browsers already. 0050 0051 From an average user's point of view a map component such as "Marble" 0052 should meet the following requirements: 0053 0054 1. FAST: 0055 0056 To allow instant access and usage as a widget the Marble Widget 0057 should start up instantly and be ready for use within 2-3 0058 seconds. So "application" startup time should always be kept as 0059 low as possible. 0060 0061 Technically this means that the Marble Widget needs to be heavily 0062 optimized for start up times and should have a minimal number of 0063 dependencies (as an increasing amount of libraries will slow down 0064 the application's launch). 0065 0066 Most other virtual globes have startup times of 15-30 secs. 0067 That's just an eternity to wait for if you just want to look up 0068 something. 0069 0070 0071 2. VISUALLY APPEALING: 0072 0073 The maps drawn by Marble Widget should adhere to visual 0074 cartographic standards and should look appealing. Usually people 0075 prefer the 3D globe view as it looks more natural, mostly because 0076 of minimal distortion and because it looks more "advanced". It 0077 should be possible to easily print the maps and to embed them into 0078 documents without getting a pixel mess that is hard to decipher. 0079 0080 Most other virtual globes don't offer good printing support and 0081 the graphical representation most of the time is just limited to 0082 satellite views that are often labeled pretty badly. Web based 0083 solutions (such as Google Maps) are quite static in their 0084 appearance and are limited in terms of possible modification. 0085 0086 0087 3. EASE OF USE: 0088 0089 Another very important aspect is usability: The feature set should 0090 cover the use cases of the primary target user only. 3D flights 0091 are pretty exciting for users that want to be entertained. 0092 However most users don't need them, don't have the time to 0093 experiment with them or don't even discover that feature. So 0094 focusing on the top-bottom view exclusively ("2.5D") makes sense 0095 for Marble. 0096 0097 Maps should be easy to read. In a lot of cases this will mean 0098 that the flat projection ("equirectangular projection" / "plate 0099 carrée") is more convenient (e.g. in a timezone chooser dialog). 0100 0101 I personally consider Google Earth's interface too complex for 0102 most users we are aiming for. Google Maps on the other hand seems 0103 too simple to me and also has a slight annoyance factor due to its 0104 web based nature. 0105 0106 0107 4. MINIMAL HARDWARE/SOFTWARE REQUIREMENTS: 0108 0109 The Marble Widget should work at usable speed out of the box on 0110 all possible hardware the desktop environment is running on. It 0111 should always show exactly the same output independent of the 0112 hardware. During installation modifications to the system should 0113 stay as low as possible. 0114 0115 This is an important point as people will simply neglect a 0116 solution if it's too painful to install or results in other 0117 unnecessary challenges during configuration. Unfortunately many, 0118 if not most, computer systems out there don't offer decent 3D 0119 hardware acceleration for graphics. So the solution we are aiming 0120 for should not depend on 3D hardware acceleration, although we 0121 certainly might want to offer solutions such as an OpenGL backend 0122 as an option. Also the amount of software needed to install the 0123 map component should stay as low as possible (see 1.) ). 0124 0125 0126 5. OFFLINE USAGE: 0127 0128 The Marble Widget should offer a minimal data set that is 0129 specifically edited and compiled for offline usage. This is 0130 especially useful in countries where internet access is restricted 0131 or expensive. Online usage should cover incremental downloading 0132 of texture tiles, vector data (e.g. OpenStreetMap) and wikipedia 0133 articles. 0134 Concerning offline geographical data Marble intends to deliver the 0135 "biggest bang for the byte" and provide as much high quality 0136 information per byte as possible. 0137 0138 For all information that goes beyond map labels ("Marble Almanac") 0139 we have started cooperation with the Wikipedia Offline Reader 0140 Project. 0141 0142 0143 6. FREE SOFTWARE & OPEN STANDARDS: 0144 0145 The Marble Widget is free software and should use a small set of 0146 open standards for communication with other applications at 0147 runtime and to save data to the storage medium. The open KML file 0148 format used by Google Earth is probably the most popular file 0149 format these days to geo reference data. Through "feeding" KML 0150 streams to the map component, applications are offered a simple 0151 "programming" interface to control the map's appearance and 0152 behaviour. All Information displayed on the map widget should be 0153 covered by free licenses using sources such as NASA or 0154 OpenStreetMap. 0155 0156 Many other virtual globes are proprietary and are using commercial 0157 geo data that is considered "non-free" (as it isn't freely 0158 redistributable). 0159 0160 0161 The Marble Universe 0162 =================== 0163 0164 Apart from the Marble Widget (which is implemented using the Qt4.2 0165 library only) there are other planned member components of the Marble 0166 universe: 0167 0168 1. "Marble Desktop Globe": 0169 0170 KDE 4 application for KDE-EDU: This "reference" application is 0171 meant to show off much of Marble's full potential. At the current 0172 point of time it's the next logical step as educational 0173 applications don't need to cover the data in full detail to be 0174 useful. Once it reaches maturity the Marble backend could be 0175 moved into a more central place, e.g. kdelibs/base. 0176 0177 2. "Marble Widget": 0178 0179 Can be used in different applications like KStars, KControl, 0180 DigiKam, KGeography, Kopete, Addressbook, Risk-Game, KWorldClock, 0181 Traceroute, Plasma Weather Applet, and so on. Depending on the use case 0182 it can have different appearances: 0183 - "normal" widget 0184 - selection dialog 0185 - developer mode 0186 0187 3. "Marble Framework": 0188 0189 A framework of geo services for the desktop. This should cover a 0190 "position provider" backend like GPS, hostip.info, track turtle, 0191 and information services ( "Marble Almanac" ). 0192 0193 0194 Torsten Rahn 0195 0196 0197 References: 0198 0199  as an interesting read see the discussion section at 0200 http://www.earthslot.org/vgconference/VGconference_results.php 0201 0202  for a nice introduction into virtual globes and a 0203 non-comprehensive list of them see the article at Wikipedia 0204 http://en.wikipedia.org/wiki/Virtual_Globe 0205 0206  www.freegis.org provides a nice software overview on Free 0207 Geographic Information Systems 0208 0209  KML 2.1 Reference available at: 0210 http://earth.google.com/kml/kml_tags_21.html