A proposed standard for incrementally parseable GeoJSON data.
Large JSON files pose a problem that is well explained in the motivation for the JSON Text Sequences RFC 7464.
The JavaScript Object Notation (JSON) [RFC7159] is a very handy serialization format. However, when serializing a large sequence of values as an array, or a possibly indeterminate-length or never-ending sequence of values, JSON becomes difficult to work with.
Consider a sequence of one million values, each possibly 1 kilobyte when encoded -- roughly one gigabyte. It is often desirable to process such a dataset in an incremental manner: without having to first read all of it before beginning to produce results. Traditionally the way to do this with JSON is to use a "streaming" parser, but these are neither widely available, widely used, nor easy to use.
GeoJSON has exactly this problem with sequences of features, amplified by the large arrays of coordinates of each feature.
JSON Text Sequences provides a standard for dealing with this problem.
This document describes the concept and format of "JSON text sequences", which are specifically not JSON texts themselves but are composed of (possible) JSON texts. JSON text sequences can be parsed (and produced) incrementally without having to have a streaming parser (nor streaming encoder).
GeoJSON Feature Sequences are a straightforward adaptation of JSON Text Sequences. A GeoJSON Text Sequence is a document containing multiple GeoJSON texts that can be parsed and produced incrementally.
In a nutshell, GeoJSON Texts Sequences proposes that one may "explode" the following GeoJSON FeatureCollection,
{ "type": "FeatureCollection",
"features": [
{ "type": "Feature",
"geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
"properties": {"prop0": "value0"}},
{ "type": "Feature",
"geometry": {
"type": "LineString",
"coordinates": [
[102.0, 0.0], [103.0, 1.0], [104.0, 0.0], [105.0, 1.0]]},
"properties": {
"prop0": "value0",
"prop1": 0.0}},
{ "type": "Feature",
"geometry": {
"type": "Polygon",
"coordinates": [
[[100.0, 0.0], [101.0, 0.0], [101.0, 1.0],
[100.0, 1.0], [100.0, 0.0] ]]},
"properties": {
"prop0": "value0",
"prop1": {"this": "that"}}}]}
into a document containing 3 separate JSON texts delimited by a leading ASCII character RS "0x1e" (represented by "RS" below).
RS{ "type": "Feature", "geometry": {"type": "Point",
"coordinates": [102.0, 0.5]}, "properties": {"prop0": "value0"}}
RS{ "type": "Feature", "geometry": {"type": "LineString",
"coordinates": [[102.0, 0.0], [103.0, 1.0], [104.0, 0.0],
[105.0, 1.0]]}, "properties": {"prop0": "value0", "prop1": 0.0}}
RS{ "type": "Feature", "geometry": {"type": "Polygon",
"coordinates": [[[100.0, 0.0], [101.0, 0.0], [101.0, 1.0],
[100.0, 1.0], [100.0, 0.0]]]}, "properties":
{"prop0": "value0", "prop1": {"this": "that"}}}
Please note that this last representation is not GeoJSON anymore, because it uses more than one GeoJSON object. It is a GeoJSON Text Sequence which must be parsed accoring to the rules for JSON Text Sequences and then can be interpreted as a sequence of individual GeoJSON feature objects.
RFC 7464 (JSON Text Sequences) defines how parsers should behave on encountering malformed JSON objects and allows for pretty-printed objects, while approaches such as the ones described in https://en.wikipedia.org/wiki/JSON_Streaming#Line_delimited_JSON do not.