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Prevents the Matching getting confused when users are time-travelling.

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This commit is contained in:
Daniel J. Hofmann 2016-10-21 18:19:23 -07:00
parent ba5871cfa1
commit a933b5d949
2 changed files with 13 additions and 1 deletions
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2
docs/http.md
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@ -275,7 +275,7 @@ In addition to the [general options](#general-options) the following options are
|geometries |`polyline` (default), `geojson` |Returned route geometry format (influences overview and per step) | |geometries |`polyline` (default), `geojson` |Returned route geometry format (influences overview and per step) |
|annotations |`true`, `false` (default) |Returns additional metadata for each coordinate along the route geometry. | |annotations |`true`, `false` (default) |Returns additional metadata for each coordinate along the route geometry. |
|overview |`simplified` (default), `full`, `false` |Add overview geometry either full, simplified according to highest zoom level it could be display on, or not at all.| |overview |`simplified` (default), `full`, `false` |Add overview geometry either full, simplified according to highest zoom level it could be display on, or not at all.|
|timestamps |`{timestamp};{timestamp}[;{timestamp} ...]` |Timestamp of the input location. | |timestamps |`{timestamp};{timestamp}[;{timestamp} ...]` |Timestamp of the input location. Timestamps need to be monotonically increasing. |
|radiuses |`{radius};{radius}[;{radius} ...]` |Standard deviation of GPS precision used for map matching. If applicable use GPS accuracy.| |radiuses |`{radius};{radius}[;{radius} ...]` |Standard deviation of GPS precision used for map matching. If applicable use GPS accuracy.|
|Parameter |Values | |Parameter |Values |

12
src/engine/plugins/match.cpp
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@ -12,6 +12,8 @@
#include <cstdlib> #include <cstdlib>
#include <algorithm> #include <algorithm>
#include <functional>
#include <iterator>
#include <memory> #include <memory>
#include <string> #include <string>
#include <vector> #include <vector>
@ -123,6 +125,16 @@ Status MatchPlugin::HandleRequest(const std::shared_ptr<datafacade::BaseDataFaca
return Error("InvalidValue", "Invalid coordinate value.", json_result); return Error("InvalidValue", "Invalid coordinate value.", json_result);
} }
// Check for same or increasing timestamps. Impl. note: Incontrast to `sort(first,
// last, less_equal)` checking `greater` in reverse meets irreflexive requirements.
const auto time_increases_monotonically = std::is_sorted(
parameters.timestamps.rbegin(), parameters.timestamps.rend(), std::greater<>{});
if (!time_increases_monotonically)
{
return Error("InvalidValue", "Timestamps need to be monotonically increasing.", json_result);
}
// assuming radius is the standard deviation of a normal distribution // assuming radius is the standard deviation of a normal distribution
// that models GPS noise (in this model), x3 should give us the correct // that models GPS noise (in this model), x3 should give us the correct
// search radius with > 99% confidence // search radius with > 99% confidence