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Manuel Fuhr 2021-11-30 18:41:50 +01:00
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misc/readmes/profile_developers_guide.md
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@ -4,51 +4,43 @@ Profile developers guide - Technical reference for BRouter profile scripts
The tag-value lookup table
--------------------------
Within the routing data files (rd5), tag information
is encoded in a binary bitstream for the way tags and
the node tags each.
Within the routing data files (rd5), tag information is encoded in a binary
bitstream for the way tags and the node tags each.
To encode and decode to/from this bitstream, a lookup
table is used that contains all the tags and values
that are considered for encoding.
To encode and decode to/from this bitstream, a lookup table is used that
contains all the tags and values that are considered for encoding.
For each tag there are 2 special values:
- `<empty>` if the tag is not set or the value is empty
- `unknown` if the value is not contained in the table
Each value can have optional *aliases*, these alias
values are encoded into the same binary value as the
associated primary value.
Each value can have optional *aliases*, these alias values are encoded into the
same binary value as the associated primary value.
A profile must use the primary value in expressions, as
aliases trigger a parse error. E.g. if there is a line
in `lookups.dat` file:
A profile must use the primary value in expressions, as aliases trigger a parse
error. E.g. if there is a line in `lookups.dat` file:
`bicycle;0001245560 yes allowed`
then a profile must use `bicycle=yes`, as `bicycle=allowed`
gives an error.
then a profile must use `bicycle=yes`, as `bicycle=allowed` gives an error.
The numbers in the lookup table are statistical
information on the frequency of the values in the
map of Germany - these are just informational and
are not processed by BRouter.
The numbers in the lookup table are statistical information on the frequency of
the values in the map of Germany - these are just informational and are not
processed by BRouter.
Context-Separation
------------------
Way-tags and Node-Tags are treated independently,
so there are different sections in the lookup table
as well as in the profile scripts for each context.
The special tags: `---context:way` and `---context:node`
mark the beginning of each section.
Way-tags and Node-Tags are treated independently, so there are different
sections in the lookup table as well as in the profile scripts for each context.
The special tags: `---context:way` and `---context:node` mark the beginning of
each section.
An exception from context separation is the node-context,
where variables from the way-context of the originating
way can be accessed using the `way:` prefix. For the
variable nodeaccessgranted there's an additional
legacy-hack to access it as a lookup value without prefix:
An exception from context separation is the node-context, where variables from
the way-context of the originating way can be accessed using the `way:` prefix.
For the variable nodeaccessgranted there's an additional legacy-hack to access
it as a lookup value without prefix:
`if nodeaccessgranted=yes then ...`
@ -56,19 +48,17 @@ while in the general case the prefixed expressions are variables:
`if greater way:costfactor 5 then ...`
In the profile scripts there is a third context `global`
which contains global configuration which is shared for
all contexts and is accessible by the routing engine.
In the profile scripts there is a third context `global` which contains global
configuration which is shared for all contexts and is accessible by the routing
engine.
The variables from the `global` section in the profile
scripts are read-only visible in the `way` and
`node` sections of the scripts.
The variables from the `global` section in the profile scripts are read-only
visible in the `way` and `node` sections of the scripts.
Predefined variables in the profile scripts
-------------------------------------------
Some variable names are pre-defined and accessed by
the routing engine:
Some variable names are pre-defined and accessed by the routing engine:
- for the global section these are:
@ -88,30 +78,29 @@ the routing engine:
- `validForFoot`
- `validForCars`
- 2 variables to change the heuristic
coefficients for the 2 routing passes
( <0 disables a routing pass )
- 2 variables to change the heuristic coefficients for the 2 routing passes (
<0 disables a routing pass )
- `pass1coefficient`
- `pass2coefficient`
- 3 variables to influence the generation of turn-instructions
- `turnInstructionMode` 0=none, 1=auto-choose, 2=locus-style, 3=osmand-style
- `turnInstructionMode` 0=none, 1=auto-choose, 2=locus-style,
3=osmand-style
- `turnInstructionCatchingRange` default=40m
- `turnInstructionRoundabouts` default=true generate explicit roundabout hints
- `turnInstructionRoundabouts` default=true generate explicit roundabout
hints
- variables to modify BRouter behaviour
- `processUnusedTags` default=false
If an OSM tag is unused within the profile,
BRouter totally ignores the tag existence.
Skipping unused tags improves BRouter speed.
As a side effect, the tag is not even listed
in the route segment table nor the table exported as CSV.
Setting it to true/1, Brouter-web Data page will list
all tags present in the RD5 file.
If an OSM tag is unused within the profile, BRouter totally ignores the
tag existence. Skipping unused tags improves BRouter speed. As a side
effect, the tag is not even listed in the route segment table nor the
table exported as CSV. Setting it to true/1, Brouter-web Data page will
list all tags present in the RD5 file.
- for the way section these are
@ -133,21 +122,18 @@ Operators of the profile scripts
The profile scripts use polish notation (operator first).
The `assign` operator is special: it can be used
only on the top level of the expression hierarchy
and has 2 operands:
The `assign` operator is special: it can be used only on the top level of the
expression hierarchy and has 2 operands:
`assign <variable-name> <expression>`
It just assigns the expression value to this
variable (which can be a predefined variable or
any other variable, which in this case is defined
implicitly). The expression can be a complex expression
using other operators.
It just assigns the expression value to this variable (which can be a predefined
variable or any other variable, which in this case is defined implicitly). The
expression can be a complex expression using other operators.
All other operators can be used recursively to an unlimited
complexity, which means that each operand can be a composed
expression starting with an operator and so on.
All other operators can be used recursively to an unlimited complexity, which
means that each operand can be a composed expression starting with an operator
and so on.
All expressions have one of the following basic forms:
@ -158,13 +144,13 @@ All expressions have one of the following basic forms:
- `<2-op-operator> <operand> <operand>`
- `<3-op-operator> <operand> <operand> <operand>`
- A numeric value is just a number, floating point, with `.` as
decimal separator. Boolean values are treated as numbers as well,
with `0` = `false` and every nonzero value = `true`.
- A numeric value is just a number, floating point, with `.` as decimal
separator. Boolean values are treated as numbers as well, with `0` = `false`
and every nonzero value = `true`.
- A lookup match has the form `<tag-name>=<value>`, e.g. `highway=primary`
Only the primary values can be used in lookup-matches, not aliases.
The `<empty>` value is referred to as an empty string, e.g. `access=`
- A lookup match has the form `<tag-name>=<value>`, e.g. `highway=primary` Only
the primary values can be used in lookup-matches, not aliases. The `<empty>`
value is referred to as an empty string, e.g. `access=`
- 1 Operand operators are:
@ -188,26 +174,26 @@ All expressions have one of the following basic forms:
- `switch <boolean-expression> <true-expression> <false-expression>`
So the switch expression has a numeric value which is the
true-expression if the boolean expression is true, the
false-expression otherwise.
So the switch expression has a numeric value which is the true-expression if
the boolean expression is true, the false-expression otherwise.
Syntactic Sugar
---------------
To improve the readablity of the profile scripts, some syntactic variations
are possible:
To improve the readablity of the profile scripts, some syntactic variations are
possible:
- if then else: `if` can be used instead of the `switch` operator, if the
additional keywords `then` and `else` are placed between the operators:
`if <boolean-expression> then <true-expression> else <false-expression>`
- Parentheses: each expression can be surrounded by parentheses: `(<expression>)`
- Parentheses: each expression can be surrounded by parentheses:
`(<expression>)`
Please note that the profile syntax, due to the polish notation, does not
need parentheses, they are always optional. However, if there are parentheses,
the parser checks if they really match the expression boundaries.
Please note that the profile syntax, due to the polish notation, does not need
parentheses, they are always optional. However, if there are parentheses, the
parser checks if they really match the expression boundaries.
- or-ing lookup-matches: the pipe-symbol can be used as a short syntax for
lookup matches where more than one value is accepted for a key:
@ -219,42 +205,42 @@ are possible:
- boolean constants: `true` and `false` can be used instead of 1 and 0
Please note that the tokenizer always expects blank space to separate
symbols and expressions so it is not allowed to place parentheses or
the `=` symbol without separating blank space!
Please note that the tokenizer always expects blank space to separate symbols
and expressions so it is not allowed to place parentheses or the `=` symbol
without separating blank space!
The initial cost classifier
---------------------------
To trigger the addition of the `initialcost`, another variable is used:
`initialclassifier` - any change in the value of that variable leads
to adding the value of `initialcost`.
`initialclassifier` - any change in the value of that variable leads to adding
the value of `initialcost`.
Initial cost is used typically for a ferry, where you want to apply
a penalty independent of the length of the ferry line.
Initial cost is used typically for a ferry, where you want to apply a penalty
independent of the length of the ferry line.
Another useful case may be an initial cost for bicycle mounting/dismounting,
having set an initialclassifier for ways without bicycle access, with high initialcost.
For backward compatibility, if `initialclassifier` = 0, it is replaced
by the costfactor.
having set an initialclassifier for ways without bicycle access, with high
initialcost. For backward compatibility, if `initialclassifier` = 0, it is
replaced by the costfactor.
The priority classifier
-----------------------
`priorityclassifier` is a BRouter numerical parameter
calculated for ways and used for generation of pictogram/voice navigation instructions.
`priorityclassifier` is a BRouter numerical parameter calculated for ways and
used for generation of pictogram/voice navigation instructions.
Higher values means the more significant (noticeable) way,
as far as it can be predicted from OSM data.
Higher values means the more significant (noticeable) way, as far as it can be
predicted from OSM data.
To avoid a navigation instruction flood, it was decided
that the instructions are provided only if:
To avoid a navigation instruction flood, it was decided that the instructions
are provided only if:
1. You are supposed to turn at a crossroad/junction
and some other ways having the same or higher `priorityclassifier` value.
1. You are supposed to turn at a crossroad/junction and some other ways having
the same or higher `priorityclassifier` value.
2. You are supposed to go straight ahead
and some other ways having the higher `priorityclassifier` value.
2. You are supposed to go straight ahead and some other ways having the higher
`priorityclassifier` value.
The elevation buffer ( From Poutnik's glossary )
------------------------------------------------
@ -265,21 +251,22 @@ With related 3 internal BRouter variables:
- `elevationmaxbuffer`
- `elevationbufferreduce`
the Elevation Buffer is BRouter feature to filter elevation noise along the route.
It may be real, or caused by the artefacts of used SRTM elevation data.
the Elevation Buffer is BRouter feature to filter elevation noise along the
route. It may be real, or caused by the artefacts of used SRTM elevation data.
From every elevation change is at the first place cut out amount `10*up/downhillcutoff`
per every km of the way length. What remains, starts to accumulate in the buffer.
IF cutoff demand of elevation per length is not saturated from incoming elevation,
it is applied on elevation remaining in the buffer as well.
From every elevation change is at the first place cut out amount
`10*up/downhillcutoff` per every km of the way length. What remains, starts to
accumulate in the buffer. IF cutoff demand of elevation per length is not
saturated from incoming elevation, it is applied on elevation remaining in the
buffer as well.
E.g. if the way climbs 20 m along 500 m, and `uphillcutoff=3.0`, then `10*3.0*0.5 km = 15 m`
is taken away and only remaining 5 m accumulates. But if it climbed only 10 m
on those 500 m, all 10 m would be *swallowed* by cutoff,
E.g. if the way climbs 20 m along 500 m, and `uphillcutoff=3.0`, then
`10*3.0*0.5 km = 15 m` is taken away and only remaining 5 m accumulates. But if
it climbed only 10 m on those 500 m, all 10 m would be *swallowed* by cutoff,
together with up to 5 m from the buffer, if there were any.
When elevation does not fit the buffer of size `elevationmaxbuffer`,
it is converted by up/downhillcost ratio to Elevationcost portion of Equivalentlength.
When elevation does not fit the buffer of size `elevationmaxbuffer`, it is
converted by up/downhillcost ratio to Elevationcost portion of Equivalentlength.
Up/downhillcostfactors are used, if defined, otherwise costfactor is used.
- `elevationpenaltybuffer` - default 5(m).
@ -315,43 +302,41 @@ All slopes within 0 .. 1.5% are swallowed by the cutoff.
- For slope 1.75%, there will remain 0.25%.
That saturates the elevationbufferreduce 0.5% by 50%. That gives Way
cost to be calculated 50% from costfactor and 50% from
Up/downhillcostfactor. Additionally, 0.25% gives 2.5m per 1km,
converted to 2.5*60 = 150m of Elevationcost.
That saturates the elevationbufferreduce 0.5% by 50%. That gives Way cost to
be calculated 50% from costfactor and 50% from Up/downhillcostfactor.
Additionally, 0.25% gives 2.5m per 1km, converted to 2.5*60 = 150m of
Elevationcost.
- For slope 2.0%, there will remain 0.5%.
That saturates the elevationbufferreduce 0.5% by 100%. That gives Way
cost to be calculated fully from `up/downhillcostfactor`.
Additionally, 0.5% gives 5m per 1km, converted to 5*60 = 300m of
Elevationcost. Up to slope 2.0% the buffer value stays at 5m =
`elevationpenaltybuffer`.
That saturates the elevationbufferreduce 0.5% by 100%. That gives Way cost to
be calculated fully from `up/downhillcostfactor`. Additionally, 0.5% gives 5m
per 1km, converted to 5*60 = 300m of Elevationcost. Up to slope 2.0% the
buffer value stays at 5m = `elevationpenaltybuffer`.
- For slope 2.5%, there will remain 1.0% after cutoff subtract, and 0.5%
after the buffer reduce subtract.
- For slope 2.5%, there will remain 1.0% after cutoff subtract, and 0.5% after
the buffer reduce subtract.
The remaining 0.5% accumulates in the buffer by rate 5 m/km. When the
buffer is full (elevationmaxbuffer), the elevation transforms to
elevationcost by full rate of 1.0%, i.e. 10 m/km, giving elevationcost
10*60=600 m/km.
The remaining 0.5% accumulates in the buffer by rate 5 m/km. When the buffer
is full (elevationmaxbuffer), the elevation transforms to elevationcost by
full rate of 1.0%, i.e. 10 m/km, giving elevationcost 10*60=600 m/km.
Technical constraints
---------------------
- The costfactor is required to be >= 1, otherwise the cost-cutoff
logic of the routing algorithm does not work and you get wrong results.
- The costfactor is required to be >= 1, otherwise the cost-cutoff logic of the
routing algorithm does not work and you get wrong results.
- The profile should be able to find a route with an average costfactor
not very much larger than one, because otherwise the routing algorithm
will not find a reasonable cost-cutoff, leading to a very large
search area and thus to long processing times.
- The profile should be able to find a route with an average costfactor not very
much larger than one, because otherwise the routing algorithm will not find a
reasonable cost-cutoff, leading to a very large search area and thus to long
processing times.
- Forbidden ways or nodes must be treated as very high cost, because
there is no *forbidden* value. Technically, values >= 10000 for a
(way-)costfactor, and >= 1000000 for a nodes `initalcost` are treated
as infinity, so please use these as the *forbidden* values.
- Forbidden ways or nodes must be treated as very high cost, because there is no
*forbidden* value. Technically, values >= 10000 for a (way-)costfactor, and >=
1000000 for a nodes `initalcost` are treated as infinity, so please use these
as the *forbidden* values.
- Ways with costfactor >= 10000 are considered as if they did not exist at all.
@ -362,52 +347,49 @@ Technical constraints
Developing and debugging scripts
--------------------------------
For developing scripts, the *brouter-web* web-application is your
friend. You can use that either online at https://brouter.de/brouter-web
or set up a local installation.
For developing scripts, the *brouter-web* web-application is your friend. You
can use that either online at https://brouter.de/brouter-web or set up a local
installation.
*brouter-web* has a window at the lower left corner with a *Profile*
and a *Data* tab. Here, you can upload profile scripts and see
the individual cost calculations per way-section in the *Data*-tab.
*brouter-web* has a window at the lower left corner with a *Profile* and a
*Data* tab. Here, you can upload profile scripts and see the individual cost
calculations per way-section in the *Data*-tab.
For profile debugging activate `assign processUnusedTags = true`
to see all present OSM tags on the Data tab, not just those used in the tested profile.
For profile debugging activate `assign processUnusedTags = true` to see all
present OSM tags on the Data tab, not just those used in the tested profile.
Lookup-Table evolution and the the *major* and *minor* versions
---------------------------------------------------------------
The lookup-table is allowed to grow over time, to include more tags
and values as needed. To support that evolution, it carries a major
and a minor version number. These numbers are also encoded into
the routing data files, taken from the lookups.dat that is used
to pre-process the routing data files.
The lookup-table is allowed to grow over time, to include more tags and values
as needed. To support that evolution, it carries a major and a minor version
number. These numbers are also encoded into the routing data files, taken from
the lookups.dat that is used to pre-process the routing data files.
A major version change is considered to always break compatibility
between the routing datafiles and the lookup table.
A major version change is considered to always break compatibility between the
routing datafiles and the lookup table.
A minor version change keeps the routing data files and the lookup-table
compatible in both directions, using the following rules:
- if the data contains a key that is not contained in the lookup
tables, it is ignored
- if the data contains a key that is not contained in the lookup tables, it is
ignored
- if the data contains a value that is not contained in the lookup
tables (but its key is known) that value is treated as `unknown`
- if the data contains a value that is not contained in the lookup tables (but
its key is known) that value is treated as `unknown`
- if a profile uses a key that is not present in the data,
it sees empty (=unset) values for that key
- if a profile uses a key that is not present in the data, it sees empty
(=unset) values for that key
- if a profile uses a value that is not present in the data,
lookup matches for that value are always false.
- if a profile uses a value that is not present in the data, lookup matches for
that value are always false.
For a minor version change it is required that tags are only
appended at the end of the table (or replace one of the dummy
tags located between the way-tags and the relation pseudo-tags),
and that values are only appended at the end of the value lists.
This is because the routing data files address tags and values
by their sequence numbers, so changing sequences would produce
garbage data.
For a minor version change it is required that tags are only appended at the end
of the table (or replace one of the dummy tags located between the way-tags and
the relation pseudo-tags), and that values are only appended at the end of the
value lists. This is because the routing data files address tags and values by
their sequence numbers, so changing sequences would produce garbage data.
Other resources
---------------