Planetary Cartography – Activities and Current Challenges

Maps are one of the most important tools for communicating geospatial information between producers and receivers. Geospatial data, tools, contributions in geospatial sciences, and the communication of information and transmission of knowledge are matter of ongoing cartographic research. This applies to all topics and objects located on Earth or on any other body in our Solar System. In planetary science, cartography and mapping have a history dating back to the roots of telescopic space exploration and are now facing new technological and organizational challenges with the rise of new missions, new global initiatives, organizations and opening research markets. The focus of this contribution is to introduce the community to the field of planetary cartography and its historic foundation, to highlight some of the organizations involved and to emphasize challenges that Planetary Cartography has to face today and in the near future.


Overview and Introduction
Cartography is the science and art of filtering and compiling spatial data into map information and to communicate complex spatial relationships and interdependences by advanced visualization techniques.It also provides cartographic analysis toolsets to arrive at mapping results.Planetary Cartography forms an integral part of cartography and has found its manifestation in governmental activities, community efforts, professional organizations, and, in re-cent years, private activities.That activity substantiated with the revival of planetary exploration in the early 2000s when Europe visited the Moon for the first time, and the US launched a number of exploration mission.With the success of Asian spacecraft missions to the Moon and Mars joining the global planetary exploration endeavor, Planetary Cartography is increasingly becoming a global collaborative effort with Planetary Mapping being one of its main tools to accomplish the goals.Planetary Cartography does not only provide the means to create science products after successful termination of a planetary mission by distilling data into maps.It also provides the basis to support planning (e.g., landing-site se-lection, orbit observation, traverse planning) and to facilitate mission conduct during the lifetime of a mission (e.g., observation tracking and hazard avoidance).After a mission's lifetime, information is stored in data archives -and eventually into maps and higher-level data products -to form a basis for research and for new scientific and engineering studies.The complexity of such tasks increases with every new dataset that has been put on this stack of in-formation, and in the same way as the complexity of autonomous probes increases, also tools that support these challenges require new levels of sophistication.As of today, hundreds of planetary maps have been produced and published during a number of different frame-work programs and projects.Therein, different mapping efforts exist, either on a national level or as collaboration between groups participating as investigators in mapping missions.However, coordination of such tasks does not end with the compilation and publication of a set of maps.Coordination may be considered successfully only when mapping products have been provided to upcoming generations of researchers and mappers to allow efficient re-use of a new sustainable data basis.In order to accomplish this, mapping infrastructure, workflows, communication paths and validation tools have to be developed and made available.Current work covering the status of planetary cartography is described by Pędzich and Latuszek (2014), Kirk (2016), Lawrence et al. (2016), Nass et al. (2016), andWilliams (2016).The focus of this brief contribution is to summarize the history and recent activities in Planetary Cartography across the globe and to highlight some of the issues and opportunities the community is currently facing.By this we would like to invite cartographers and researchers interested in this field to join this community and to jointly start thinking about how we can jointly solve some of these challenges.

Distillation of Information, Abstraction and Visualization
Visualization of data in general, and visualization of research data in particular, represents a simplified view on the real world, covering complex situations as well as the relationship between these (Ware 2004, Mazza 2009).The process to accomplish this can be divided into four major parts: (1) data pre-processing and transformation, (2) visual mapping, (3) generation of views, and (4) perception/cognition.The mapping process in Planetary Cartography is comparable to established processes commonly employed in terrestrial cartographic workflows that are described as so-called visualization pipeline (e.g., Haber andMcNabb 1990, Carpendale 2003, figure 1).
Figure 1 Visualization Pipeline (cf.Haber andMcNabb 1990, Carpendale 2003) This process is independent of actual production techniques and methods and describes different steps from acquisition and filtering of raw data (input), abstraction and generalization of information (distillation), and rendering, i.e. visualization of results (output).The last step in this pipeline is the recursion and by that the manipulation of previous processing steps: input and distillation (see figure 2).
Mapping of physical surfaces represents a special way of spatial data visualization within its scientific context as it does not show an objective visualization of a situation, but rather a subjective distinction of individual surface structures, units, and objects (see also Haber and McNabb 1990).This interpretation will generally be conducted by experts in their topical field whose expertise allows isolating, differentiating, and describing individual planetary objects based on remote-sensing data to reconstruct processes which shaped the current character of a surface.In planetary research and mapping, geographic information system technology (GIST) has been commonly employed to accomplish this since the early 2000s.
Figure 2. Overview of processes during mapping.

Historical Outline
Extraterrestrial mapping dates back to shortly after the invention of the telescope at the beginning of the 17th century which marked a milestone in planetary exploration.These maps of the Moon (van Langren in 1645, Hevelius in 1647, Grimaldi and Riccioli in 1651) offered different approaches in visual and toponymic representation of an extraterrestrial landscape.Many improvements were introduced during the upcoming centuries and extraterrestrial mapping became a scientific discipline with map products similar in appearance and style as their terrestrial counterparts (Blagg and Müller 1935;Sadler 1962;Whitaker et al. 1963;Slipher 1962;Mason and Hackman, 1961;Shoemaker 1961;Portee, 2013).Despite this success and many advances in the field of Earth-based telescopic observations and mapping, detailed topographic features and landforms could only be mapped from observation plat-forms located on spacecraft.This process started with the first set of pictures received from the far side of the Moon (Luna 3;Babarashov et al. 1960), and Mars (Mariner 6;Davies et al. 1970).Venus was first mapped in detail by the Venera probes and results were published as a series of 27 map sheets (GUGK 1988) and the first comprehensive cartographic atlas of multiple Solar System bodies was published by Shingareva et al. (1992).China joined the countries with planetary mapping centers with the publication of several maps, atlases and globes using the images from the Chinese Chang'E lunar probe series (e.g., Compiling Committee 2010).Global topographic data of variable resolution are now available from laser and radar altimetry, stereo photogrammetry, stereo photoclinometry for Mercury, Venus, the Moon, Mars, Ceres, Vesta, Titan, and Phobos.Following the long-employed method of replicating images using hand drawing maps showing the topography of planets and moons used airbrush technique and manual interpretation of several sets of photographs.This was re-placed by digital image mosaicking techniques in the 1990s.Parallel to terrestrial developments since middle 1990 modern and digital mapping techniques within vector-and raster-based graphic software arose.This includes the first efforts of GIS-based data integration and mapping in planetary sciences.Since then, a few developments and approaches came up to make the usage of GI technologies more efficient for planetary mapping and cartography representation (e.g., Hare and Tanaka 2001;Hare et al. 2009;van Gasselt and Nass 2011;Nass and van Gasselt 2011;Frigeri 2011;Hare et al. 2015).The most comprehensive review on all aspects of planetary cartography was published by Snyder (1982Snyder ( , 1987)), and Greeley and Batson (1990).Radar mapping techniques are discussed in Ford et al. (1993).For detailed summaries on the development and evolution of Planetary Cartography the reader is referred to Shevchenko et al. (2016) for the history of Soviet and Russian planetary cartography, and to Jin (2014) for Chinese Lunar mapping results.History of planetary mapping is discussed in e.g., Kopal and Carder (1974) and Morton (2002), and recent planetary cartographic techniques and tools are reviewed in Beyer (2015) and Hare et al. (2017, in prep.).

Planetary Cartography Groups
This chapter introduces institutes and groups working in the field of Planetary Cartography and Mapping.Some of them have a long history in planetary cartography while others represent more recent efforts.Their activities are usually organized on a national level but they are internationally related to each other through research cooperation and collaborative projects.This overview does not qualify to be complete and to list all active organizations and groups.It should provide a crosssection covering main institutions as well as groups and initiatives.

Institutes and Facilites
In the United States, the Astrogeology Science Center (ACS) was established in Flagstaff, Arizona on July 1, 1963 as a research facility of the United State Geological Survey (USGS) (Schaber 2005) through the efforts and re-quests of several geoscientists and cartographers, perhaps most notably geologist E. Shoemaker.The USGS and the NASA agreed on the benefits of a research center that focused on compiling planetary maps, developing observational instrumentation, and training both astronauts and fellow researchers.Therein, location in Flagstaff proved an advantageous based on existing planetary research community, proximity to lunarobserving telescopes, as well as geologically diverse, yet highly accessible analog terrain.The USGS ASC has evolved over the past five decades in response not only to the changing needs of NASA and the planetary science community but also to the increased volume and diversity of modern, technologically advanced data sets acquired for planetary bodies.By doing so, within the Planetary Geological Mapping Program1 (founded by NASA and coordinated by the USGS ACS) planetary maps and cartographic products were produced which reveal topography, geology, topology, image mosaics, and more.The aim of this program is to support the international research community with high-quality peerreviewed geologic maps of planetary bodies.To accomplish this and to have comparable and homogenous map results, the mapping process has been standardized and is coordinated from its beginning (usability of input data) up to final map layout, printing, publishing, and archiving (Tanaka et al. 2011).All the resulted products are available to the international scientific community and the general public as a national resource2 .
In order to handle these tasks effectively, i.e., to ensure that unnecessary duplication is reduced to a minimum, cooperation is critical, wherein multiple institutions and organizational bodies must cross collaborate.In Germany, the Institute of Planetary Research at the German Aerospace Center (DLR) in Berlin -among other groups in Germany -has been involved in a number of planetary cartographic topics since its establishment in the early 1990s.A series of Mars maps were compiled in the early 1990s (Hiller et al. 1993;Neugebauer and Dorrer 1996) in preparation of the Russian Mars-96 mission.Since that time the main focus of DLR's cartography has been put on generation of image mosaics and topographic maps.For the HRSC contribution for Mars Express (Jaumann et al., 2007) this work has been conducted also in close collaboration with groups at universities like the TU of Berlin, FU Berlin, TU Dresden, TU Munich or University Hannover.It involves production of image and topographic maps, definition of a large-scale quadrangle schema for cartographic representation of Mars (Lehmann et al. 1997;Albertz et al. 2005), or automatization of map generation processes (PIMap, Gehrke et al. 2006).A new set of cartographic products based on the integration of data from multiple orbits was produced and published recently (Gwinner et al. 2016).Controlled image and topographic data mosaics were also produced and published for Phobos (Wählisch et al. 2010(Wählisch et al. , 2014;;Willner et al. 2010Willner et al. , 2014)), or the Icy Saturnian Satellites4 (Roatsch et al. 2009).For Ceres and Vesta, global mosaics serve as base map for different atlas collections5 (e.g.Roatsch et al. 2013Roatsch et al. , 2016)).
During the last ten years the DLR has also been focusing on GIS-based mapping and tasks of processing, analyzing, archiving, and visualizing scientific results (e.g., Deuchler et al. 2004;Saiger et al. 2005)

Organizations and Initiatives
The Commission on Planetary Cartography of the International Cartographic Association (ICA) was established in 1995 with the goal of disseminating products and initiating outreach and professional projects in countries where planetary cartographic materials are scarcely available or altogether absent.The commission focuses on supporting planetary cartographic projects in emerging planetary communities.Since its formation, the commission developed three multilingual outreach map series: a series edited in Dresden (Buchroithner 1999), a Central European edition (Shingareva et al. 2005), and a special series for children (Hargitai et al. 2015).The commission members compiled the Multilingual Glossary of Planetary Cartography (Shingareva and Krasnopevsteva 2011) and the GIS-ready Integrated Database of Planetary Features (Hargitai 2016).It also developed a planetary cartographic application that can be used to compare sizes of planetary features to countries and states (Gede and Hargitai 2015) and maintains the Digital Museum of Planetary Mapping 6 .Naming of topographic features and the publication of the Gazetteer of Planetary Nomenclature are coordinated by the International Astronomical Union (IAU).It was founded in 1919 at the Constitutive Assembly of the International Research Council in Brussels, Belgium to oversee assigning names for stars, planets, moons, asteroids, comets and surface features on them (Blaauw 1994).The first goals were to normalize various systems used in Lunar and Martian nomenclatures across different countries (Blagg 1935).The current nomenclature database is managed by the USGS ASC on behalf of the IAU.In 1976, the IAU established a working group on the Cartographic Coordinates and Rotational Elements of Planets and Satellites to report triennially on the preferred volumes for the parameters of the rotation rate, spin axis, prime meridian, and reference surface for planets and satellites (Archinal 2011).This working group founded to allow the consistent data usage across many facilities, including surface exploration by robots and humans.However, the IAU's oversight does not cover other standards essential for digital mapping including common feature attributions, feature symbols, recommended mapping scales and metadata or the documentation of the data.For the U.S., this role has been filled by the Federal Geographic Data Committee (FGDC) and its recommendations are generally closely adopted by the International Standards Organization (ISO).Within the FGDC ( 2006) feature attributes and their assigned symbols for terrestrial and also planetary digital maps are de-fined (FGDC 2006).For a clear understanding of planetary maps, these symbols are primarily based on the same set of attributes and symbols as used for the Earth (see e.g., Nass 2010; Hargitai 2011).The International Society for Photogrammetry and Remote Sensing (ISPRS) working group IV/8 "Planetary Mapping and Spatial Databases" is built by the community to provide a platform for those involved in all topics of planetary cartography, such as data acquisition, processing, and information extraction from planetary remote sensing data for the mapping of celestial bodies.This also includes the evaluation and refinement of reference systems, coordinate systems, control networks, map sheet definitions, etc., and their standardization.The group organizes workshops and symposiums to exchange the latest developments in planetary mapping, cartography and remote sensing, and promotes international cooperation since 1998.After the 2016 ISPRS Congress in Prague the working group transforms to a new inter-commission group "Planetary Remote Sensing and Mapping".Different groups were originated by NASA to coordinate map requirements, recommend map series and standards, establish priorities for map production, monitor map distribution, and facilitate international cooperation in lunar mapping (PCWG 1989).The last ten years of activity within Planetary Cartography and Geologic 6 http://planetarymapping.wordpress.com.
Mapping Working Group (PCGMWG) was largely focused on monitoring and guiding the cartographic contributions of the USGS ASC.The Mapping and Planetary Spatial Infrastructure Team (MAPSIT) was formulated in 2014 as a means to reaffirm that modern cartography i.e., spatial data infrastructure (NSF 2012), fundamentally affects all aspects of scientific investigation and mission planning, regardless of the target body of interest.MAPSIT faces tremendous challenges, not the least of which is the sheer scope of modern planetary exploration, which results in a multitude of spatial parameters related to instrument types, target body characteristics, and coordinating institutions.
In addition to institutional and organizational efforts, a number of initiatives have arisen in recent years motivated not only by individuals but also by commercial entities that specialize in combining planetary (map) data with web technologies.Today, different startups and organizations offer platforms and pre-existing cartographic databases which often feature open-source mapping technologies at their core.It has made it even easier for non-GIS-specialists, researchers, or data enthusiasts to visualize, manipulate, and share their data and maps on the web (Zastrow 2015).E.g., CARTO, a company focused on web-based geospatial data visualization and analysis, collabo-rated with ESA to support an open-source outreach project intended to raise public awareness of ESA's ExoMars Rover mission through an interactive map of the candidate landing sites (Where On Mars? 7 , Manaud et al. 2015).The OpenPlanetary 8 initiative was created in 2015 (Manaud et al. 2016a) providing an online framework to help collaborate on common planetary mapping and data analysis problems, on new challenges, and to create new opportunities.Also, a number of projects funded by the European Commission are directly or indirectly relevant to planetary mapping.The largest, and one of the most long-lasting efforts, is VESPA (Erard et al. 2014(Erard et al. , 2016)), the Euro-Planet H2020 Research Infrastructure component that deals with accessibility and distribution of planetary science data from very diverse scientific domains, including a specific surface mapping task (Rossi et al. 2015).E-Infrastructure projects with broad Earth Science focus, such as EarthServer-2, include a Planetary Science component, PlanetServer (Baumann et al. 2015;Rossi et al. 2016).Rather than focusing on data searches and discovery or on-demand processing, PlanetServer primarily uses the OGC WCPS standard (Baumann et al. 2010) to perform re-al-time data analytics (Rossi et al. 2016;Marco Figuera et al. 2015).Lastly, few citizen science projects with clear planetary mapping target exist.Some of them are embedded in a broader context, such as iMars (Muller et al. 2016); others originate from experiment-driven effort (NASA MRO HiRISE), such as PlanetFour (Aye et al. 2016).Additional citizen-science efforts based on NASA LRO LROC imagery mapping include Moon Zoo (Joy et al. 2011).USGS ASC and ASI held a topical meeting in 2009 on the topic of "Geological Mapping of Mars: a workshop on new concepts and tools" (Pondrelli et al. 2011).Since then the state-of-the-art evolved significantly, not only from institutional (space agencies and surveys) perspective, but also in terms of technology, applications, and services.While planetary data mapping workshops have been held twice in the United States (coordinated by USGS ACS), ESA's Space Astronomy Centre (ESAC) supported its first Planetary GIS workshop in 2015 (Manaud et al. 2016b).

Challenges in Planetary Cartography
The standardization of cartographic methods and data products is critical for accurate and precise analysis and scientific reporting.This is more relevant today than ever before, as researchers have easy access to digital data as well as to the tools to process and analyze these various products.The life cycle of cartographic products can be short and standardized descriptions are needed to keep track of different development branches.One of our aims herein was to compartmentalize the processes of Planetary Cartography and to define, describe, and present the overall mapping process through its components breakdown.
Processes related to INPUT compartment (Figure 2) cover all aspects related to the distillation of information that allows not only to produce higher-level products but also to create a basis for their stable representation and re-usability.One of the major tasks is to establish an international map-data basis by digitizing analogue maps and by establishing a uniform structure to describe existing data allowing them to be queried and accessed.
For digital map products, a metadata description along with validation tools and platforms capable of providing access to archiving, distribution, and querying needs to be established.Standards already partially exist on a national level and some of the older higher-level map-data products are currently transferred to fit into such schemata.However, many map products exist all around the world and are distributed across different institutes.One task will be to review such products and to establish a methodological repertoire to transfer maps, to establish a common metadata scheme and to provide a common semantical basis.DISTILLATION processes ensure effective and efficient GIS-based management of data and derived map-data products in order to enable a consistent style of cartographic visualization.We identify three major tasks that are necessary to accomplish this: (1) definition and setup of rules and recommendations for GIS-based mapping process (cf.Tanaka et al. 2011); (2) advocating for GIS-based implementation and distribution of international cartographic symbol standards; (3) generating generic, modular data models for GIS-based mapping and tools for transferring existing data into these models.Efforts are currently focusing on creating a templates-based framework on evaluation and optimization of existing map templates.In particular the short lifetime of products during ongoing missions pose a considerable challenge when creating and operationally working with such models.Furthermore, recent work focuses on revising recommendations for cartographic symbols for geologic mapping.It encompasses critical review and updating of existing symbol standards for planetary geologic symbols (FGDC 2006).
OUTPUT processes cover all aspects of publishing and archiving mapping results in easily accessible archives and intuitive online interfaces and platforms.One method to achieve this is to incorporate already published maps along with their metadata into a uniform platform using a uniform format.That can be achieved by establishing metadata descriptions of maps and digital map projects that build on existing definitions and which can benefit from existing validation tools.The Planetary Data System in its version 4 has provided a flexible toolset to accomplish parts of this task in cooperation with the USGS ACS.Existing efforts covering this topic are described in e.g., Hare et al. (2011), Hare (2011), and Nass et al. (2010).
A next step is to build an internationally accessible digital map archive that includes digitized analogue maps and digital maps and mapping products.Already existing archives are provided by the USGS ACS or by the Planetary Data Set (PDS 2009).The last point in this task group covers aspects of interoperability and exchange of map pro-jects between different mapping and database systems.As different research institutes and individuals use different tools for mapping and data storage, procedures have to be found to allow conversions and also collaborative map-ping in the future.
A general aim for this Planetary Cartography group is to work on concepts and approaches to foster future cooperation between cartographers and noncartographers.Also, collaboration should focus on reducing duplication of efforts and combining limited resources in order to address technical and scientific objectives.Recently -and primarily motivated by such tasks -international cross-collaborations between our institues, critical involvement within organizations like MAPSIT or ICA, but also ongoing contribution to initiatives like VESPA have been established.This network will focus on (1) identifying and prioritizing needs of the planetary cartography community along with a strategic timeline to accomplish prioritized goals, (2) keeping track of ongoing work across the globe in the field of Planetary Cartography, and (3) identifying areas of evolving technologies and innovation deal with mapping strategies as well as output media for the dissemination and communication of cartographic results.

Footnotes
Mark footnotes in the text with a number.Place footnotes at the bottom of the page, separated from the text above it by a horizontal line 9 .
Shevchenko et al. 2016main of the Department of Lunar and Planetary Physics of Sternberg Astronomical Institute (SAI), and a number of collaborations have substantiated in this national context (e.g.,Shevchenko et al. 2016).
(Shingareva et al. 2005)cially founded: the Space Research Institute of the Academy of Sciences of the USSR (IKI).Since 1999 MIIGAiK, Dresden Technical University (Germany), Eötvös Lorànd University (ELTE) (Hungary), and the University of Western Ontario (Canada) have participated in the project Multi-language Maps of Planets and their Moons.Therein, a series of multi-language maps of planets and their moons have been created(Shingareva et al. 2005), among them maps ofMars (1999), Venus (2001), the Moon (2003),Mercury (2005),Phobos and Deimos (2006).Intense international collaborations in the course of ESA's Mars Express have resulted in Phobos special issue(Oberst et  al. 2014)and The Phobos Altas(Savinykh et al. 2015).