TOWARDS A NEW FACE FOR PLANETARY MAPS ON THE WEB. N. Manaud1, A. Nass2, S. van Gasselt3, T. Hare4, A.P. Rossi5, M. Lewando6, 1SpaceFrog Design, Toulouse, France (nicolas@spacefrog.design), 2German Aerospace Center, Institute of Planetary Research, Berlin, Germany (andrea.nass@dlr.de), 3 National Chengchi Uni-versity, Taipei, Taiwan (svg@nccu.edu.tw), 4U. S. Geological Survey, Astrogeology Team, Flagstaff, USA (tha-re@usgs.gov), 5Department of Physics and Earth Sciences, Jacobs-University Bremen, Bremen, Germany (an.rossi@jacobs-university.de), 6Independent Technologist, Cardiff, United Kingdom (info@myleslewando.com).

Introduction: In the context of the OpenPlane-

taryMap project, we are creating planetary basemaps designed to enhance the overall user experience of a wide range of web mapping applications.

The OpenPlanetaryMap (OPM) project is an com-munity-driven initiative to build the first Open Plane-tary Mapping and Social platform for planetary scien-tists, space enthusiasts, educators and storytellers [1]. The main goal of this project is to make it easy to cre-ate and share location-based knowledge and maps of Mars and other planets of our Solar System.

Figure 1. Overview of the OpenPlanataryMap plat-form and ecosystem of users and third party applica-tions.

We present here an overview of a new cartographic approach of creating a web basemap for Mars, and the first implementation of a web basemap reflecting the common understanding and picture that laymen as well as professionals might have about Mars [2]. We dis-cuss the next steps for improving our basemaps, and getting feedback and contributions from the communi-ty.

Cartographic Concept and Data Model: We

have developed a cartographic concept built on a num-ber of key questions: (1) what kind of information do we want to communicate, i.e. which picture do we want to draw of Mars, (2) who are the recipient and target audience, and (3) how can we maximize func-tionality and aesthetics with as few datasets as possi-ble.

The underlying concepts we elaborated upon are valid for any other planetary body and might be appli-cable in the same or at least very similar way.

An easily accessible global picture of Mars might be represented by one or more of its three global char-acteristics: (1) the typical red Mars colour (hue), (2) the characteristic distribution of variations of lightness values, also known as surface albedo features, i.e., the reflectance of surface materials, and (3) the global to-pography with its characteristic dichotomy separating highlands from lowlands and rougher-surface areas from smoother ones.

All of these features are discernible and distin-guishable on larger as well as smaller map scales alike.

We use a combination of (1) MOLA derived topo-

graphic data products; including a hillshade raster da-taset as qualitative basic relief representation with main illumination from the top-left, contours and to-pography vector dataset based on a reduced resolution topography raster model, (2) TES derived albedo vec-tor dataset classified into 3 classes, and (3) nomencla-ture dataset based on International Astronomical Un-ion (IAU) gazetteer, which was later adjusted and re-fined by the USGS [3].

Implementation and Usage: Using CARTO [4] as our geospatial datasets storage and visualisation plat-form and CartoCSS as styling language, we have been able to implement key elements of our cartographic concept and to produce the first vector-based basemap for Mars (see sample screenshots in Figure 2).

A dedicated CARTO Map API can then be used to serve these maps as basemap raster-tiles (following standard XYZ tiling scheme) that can be easily used in web applications using mapping javascript library (see Leaflet example below).

var layer = new L.tileLayer('https://cartocdn-

gusc.global.ssl.fastly.net/opmbuilder/api/v1/map/nam

ed/opm-mars-basemap-v0-2/0,1,2,3,4/{z}/{x}/{y}.png',

{

zoom: 3,

tms: false,

}).addTo(map).setZIndex(0);

7086.pdf4th Planetary Data Workshop 2019 (LPI Contrib. No. 2151)

Figure 2: Sample screenshots from the CARTO web map of Mars. (c) the Eastern Valles Marineris area Xanthe Terra; the area spans about 30 degrees of lon-gitude translating to 1800 km at the equator (zoom level 6), (d) the Argyre impact basin at high southern latitudes (zoom level 5), (b) sample map legend, (a) the Eastern volcanic Tharsis rise with the Valles Marineris structure and Chryse Planitia outflow area (zoom level 4). Map projection is Web Mercator which causes non-linear relationships between zoom levels and map scales.

Although CARTO can handle different map projec-tions by re-projecting datasets automatically and mak-ing them available in geodetic projection (EPSG:4326, WGS84); available basemaps and map creation are done in Web Mercator projection. Global raster da-tasets, such as hillshade, are re-projected into the Web Mercator projection (EPSG:3857) using GDAL, tiled following standard XYZ tiling scheme, and served from an Amazon S3 instance.

The CARTO Map API allows us to configure our basemap end-product so that it can be made available in different combination of layers (styled vector da-tasets or rasters, see MapConfig file [5]). For example the nomenclature layer can be accessed separately and be overlapped on top of any raster layer.

Discussion and Next Steps: Although the current

implementation in CARTO shows the proof of con-cept, we aim to provide a better experience through fast and smooth vector-rendered basemaps. CARTO serves our basemap datasets both as raster and vector tiles, but currently its Map API does not allow for vec-tor rendering. As CARTO has evolved towards vector rendering technology and Mapbox GL to render inter-active maps, we will explore these new capabilities.

We will also assess Mapbox and Maptiler as a tool to design our future vector-rendered basemaps.

As we aim to provide valuable services to the plan-etary science community, we will explore ways of making the creation of our basemaps more collabora-tive. In particular, we would like to enable map makers to apply their own style to a common open data model (similarly to the OpenMapTiles Vector Tile Schema [6]).

Our basemaps are intented to be initially used for the future web and mobile interfaces of following pro-jects: VESPA [7], PLANMAP [8], and MOCCAS [9], and we hope to attract more users.

References: [1] N. Manaud et al. (2018), “Open-

PlanetaryMap: Building the first Open Planetary Map-ping and Social platform for researchers, educators, storytellers, and the general public.”, Vol. 12, EPSC2018-78, 2018; http://openplanetarymap.org, [2] Nass et al. (2019), “Towards a new face for Planetary Maps: Design and web-based Implementation of Plan-etary Basemaps”, International Cartographic Associa-tion (accepted), [3] Hunter et al. (2016), “Feature-Linked Annotation of Lunar and Martian Nomencla-ture”, LPSC Vol. 47, p. 1558, [4] CARTO, https://carto.com, [5] “OPM Mars Basemap v0.2” MapConfig file, http://bit.ly/opm-mars-basemap-v02, [6] OpenMapTiles Vector Tile Schema, https://openmaptiles.org/schema, [7] Erard et al. (2018), “Virtual European Solar & Planetary Access (VESPA): a Virtual Observatory in Planetary Science”, Vol. 20, EGU2018-4993, 2018; http://vespa.obspm.fr, [8] Massironi et al. (2018), “Towards integrated geo-logical maps and 3D geo-models of planetary surfaces: the H2020 PLANetary MAPping project”, Vol. 20, EGU2018-18106, 2018; https://www.planmap.eu, [9] Carter et al. 2018, “A New View of Mars Aqueous Alteration: First Results from The Mars Orbital Cata-logue of Chemical Alteration Signatures (MOCCAS)”, Vol. 12, EPSC2018-49, 2018

Acknowledgment: We warmly thank Europlanet

for their initial funding through their Public Engage-ment Funding Scheme, and the CARTO team for be-lieving in this project and for their outstanding support. A special thanks go to: Javier de la Torre, Sergio Ál-varezLeiva, Andrew Hill, Stuart Lynn, Oriol Boix, Carla Iriberri, Dani Carrión, Javi Santana, Alejandro Martínez, Carlos Matallín, Mamata Akella, and Rami-ro Aznar.

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