How we make our maps

The electronic Yandex map for you and me, by and large, is a picture that can be zoomed in or out and, most importantly, that shows you what you want to find. The reality is that this map is not a single picture, but a whole system of related information about a certain territory available at maps.yandex.ru. To create this system, Yandex uses the latest satellite images, address databases and GPS tracks: geographic coordinates of vehicle trails.

Satellite images are the basis of the map. The resolution of the images that Yandex buys for its maps varies depending on the area. A detailed city map, for instance, requires high resolution images showing details as minute as road markings, while for the undeveloped areas the general images, with only large features like rivers or major highways clearly visible, are enough.

Another significant source of mapping information is the databases that list addresses with geographic coordinates, longitude and latitude, for every building. Yandex purchases these databases from providers, makes them uniform and adds them to the map. In addition, the Yandex map makers check the buildings on Yandex’s user generated map, People’s map, and, after verification, add this data to the address database. As for GPS tracks, they come from the partners of the Yandex.Traffic service, as well as from regular car owners using the application Yandex.Maps for mobile while they drive.

After all information is gathered, map makers start working on satellite images. First, they match the images to terrain using geographic coordinates. Based on the GPS data, they map four points on the image. This could be, for instance, Leninsky Prospekt crossing MKAD, a ring road around Moscow, at 55°38̒20” latitude and 37°27’35” longitude. Knowing geographic coordinates for four points is enough to find any object on a satellite image.

The next step is define mapping areas, that is decide which segments need a higher degree of detalization and which segments can be covered by a general map. The satellite images are now ready for mapping layers: road networks, buildings, bodies of water, green spaces, bus stops and other objects people may need to find on a map.

The first thing to be mapped on a satellite image is the road network. Map makers find each visible road on the image and draw lines over the roads they see using the GPS data for those segments that are not quite clear, covered by clouds, for instance. Since GPS tracks are based exactly on the vehicle’s geographic coordinates, this information gives the map makers an opportunity to locate the road.

After the roads are mapped, all other layers are ready for mapping. Making the buildings layer is the most labour-intensive, with every building on an image having to be carefully traced. Then, using geographic coordinates, map makers need to find in the database an address for every traced building. For the missing data, the Yandex map makers refer to open information sources: city web pages, developer websites or the company’s own services. Looking at a street view image on the Panoramic view layer on Yandex.Maps, for instance, the map makers can see the building’s number or check it with the information provided by the users on People’s Map. Sometimes it just takes a trip to the site.

Water bodies and green spaces are mapped together with the buildings. Map makers find and trace rivers, parks and public gardens on a satellite image. Then they outline train stations and major sights, such as the Luzhniki Olympic Complex or a circus. Yandex receives the information about the objects like these from official public sources and from its own services. The online business directory Yandex.Spravochnik, for instance, has address information for museums and exhibition centers. At this point, this is what the map looks like:

For the users to be able to find an object on the map, this object has to be named. First, using the addresses for buildings they already know, map makers give names to roads and streets where these buildings are. So, if a number of buildings along a street have the address at ‘Leo Tolstoy Street’, this street is Leo Tolstoy Street. Then, lakes, rivers, parks, train stations and major sights and landmarks get their names.

In addition to names, map makers specify the type of each object. So, a water body has to be identified as a stream or a river, or a road has to be classed as a federal highway or a dirt track. Knowing the type of an object is essential for its graphic representation: a stream is a thin line, while a river is somewhat thicker.

The map is almost ready now. It only needs to be designed graphically and approved by the authorities. Graphic designers choose the colour and the font for each object type. Then, they convert the map’s format from vector to raster. At this point the map becomes what the end users see.

To be approved for publishing, the map is printed out and submitted, first, to the Central Land Surveying and Mapping Fund, and then, to the Land Surveying and Mapping Department at the Administration of the Federal Agency for Land Inventory and Cartography. After the map receives approval from the authorities, Yandex becomes the official copyright holder and can now use it at its own discretion.

The map of Moscow and Moscow region was printed out on 1,450 А3-size sheets and in its print form weighed 13.5 kg.

The map makers keep working on the map even after it has been published. They keep it updated by regularly adding the most recent changes. User feedback is very helpful with keeping the map up-to-date, as it allows spotting inaccuracies and correcting them. The Yandex map makers always check every user report and only then make changes to the map.

The electronic map is used in many other services offered by Yandex. This map allows showing traffic conditions and planning routes, creating various information layers and building applications for mobile devices. Using the Yandex.Maps API, website owners can embed the Yandex map into their site and design geo-information service of their own.