flyover reverse engineering

Reverse-engineering Flyover (3D satellite mode) from Apple Maps. Similar work is done for Google Earth here.

Status

Roughly, these parts have been figured out:

• bootstrap of manifests
• URL structure
• authentication algorithm
• map tiling and conversion from geo coordinates
• mesh decompression (huffman tables, edgebreaker variant etc.)
• tile lookup using octree

We can authenticate URLs and retrieve textured 3D models from given coordinates (latitude, longitude).

General

Data is stored in map tiles. These five tile styles are used for Flyover:

Type	Purpose	URL structure
C3M	Texture, Mesh, Transformation(, Animation)	?(?|&)style=15&v=⓿&region=❶&x=❷&y=❸&z=❹&h=❺
C3MM 1	Metadata	?(?|&)style=14&v=⓿&part=❻&region=❶
C3MM 2	Metadata	?(?|&)style=52&v=⓿&region=❶&x=❷&y=❸&z=❹&h=❺
DTM 1	Terrain/Surface/Elevation	?(?|&)style=16&v=⓿&region=❶&x=❷&y=❸&z=❹
DTM 2	Terrain/Surface/Elevation	?(?|&)style=17&v=⓿&size=❼&scale=❽&x=❷&y=❸&z=❹

• ?: URL prefix from resource manifest
• ⓿: Version from resource manifest or altitude manifest using region
• ❶: Region ID from altitude manifest
• ❷❸❹: Map tile numbers (tiled web map scheme)
• ❺: Height/altitude index. Probably from C3MM
• ❻: Incremental part number
• ❼❽: Size/scale. Not sure where its values come from

Resource hierarchy

ResourceManifest
└─ AltitudeManifest
   ├─ C3MM
   │  └─ C3M
   └─ DTM?

Focusing on C3M(M) for now. DTMs are images with a footer and are probably used for the grid that is displayed when Maps is loading.

Code

This repository is structured as follows:

Directory	Description
cmd	command line programs
pkg	most of the actual code
proto	protobuf files
scripts	additional scripts
vendor	dependencies

Setup

Install Go 1.15.x and run:

go get -d github.com/retroplasma/flyover-reverse-engineering/...
cd "$(go env GOPATH)/src/github.com/retroplasma/flyover-reverse-engineering"

Then edit config.json:

• automatically (macOS, Linux, WSL):
  • ./scripts/get_config.sh > config.json
• faster (macOS Catalina or older):
  • ./scripts/get_config_macos.sh > config.json
• or manually (Catalina or older):
  • resourceManifestURL: from GEOConfigStore.db/com.apple.GEO.plist or GeoServices binary
  • tokenP1: from GeoServices binary (function: GEOURLAuthenticationGenerateURL)

Command line programs

Here are some command line programs that use code from pkg:

Export OBJ ^[code]

Usage:

go run cmd/export-obj/main.go [lat] [lon] [zoom] [tryXY] [tryH]

Parameter   Description       Example
--------------------------------------
lat         Latitude          34.007603
lon         Longitude         -118.499741
zoom        Zoom (~ 13-20)    20
tryXY       Area scan         3
tryH        Altitude scan     40

This exports Santa Monica Pier to ./downloaded_files/obj/...:

go run cmd/export-obj/main.go 34.007603 -118.499741 20 3 40

Optional: Center-scale OBJ using node.js script:

node scripts/center_scale_obj.js

In Blender (compatible tutorial here):

Authenticate URL ^[code]

This authenticates a URL using parameters from config.json:

go run cmd/auth/main.go [url]

Parse C3M file ^[code]

This parses a C3M v3 file, decompresses meshes, reads JPEG textures and produces a struct that contains a textured 3d model:

go run cmd/parse-c3m/main.go [file]

Parse C3MM file ^[code]

This parses a C3MM v1 file. The C3MM files in a region span octrees whose roots are indexed in the first file.

go run cmd/parse-c3mm/main.go [file] [[file_number]]

Files on macOS

• ~/Library/Containers/com.apple.geod/Data/Library/Caches/com.apple.geod/GEOConfigStore.db
  • last resource manifest url
• ~/Library/Preferences/com.apple.GEO.plist
  • last resource manifest url ~prior to catalina
• ~/Library/Caches/GeoServices/Resources/altitude-*.xml
  • defines regions for c3m urls
  • altitude-*.xml url in resource manifest
• ~/Library/Containers/com.apple.geod/Data/Library/Caches/com.apple.geod/MapTiles/MapTiles.sqlitedb
  • local map tile cache
• /System/Library/PrivateFrameworks/GeoServices.framework/GeoServices
  • resource manifest base url, networking, caching, authentication
• /System/Library/PrivateFrameworks/VectorKit.framework/VectorKit
  • parsers, decoders
• /System/Library/PrivateFrameworks/GeoServices.framework/XPCServices/com.apple.geod.xpc
  • loads GeoServices
• /Applications/Maps.app/Contents/MacOS/Maps
  • loads VectorKit

Important

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.