bif:st_within set the correct tolerance

Question

I am querying a Virtuoso store with SPARQL, and I want to retrieve some layer that are near a wkt geometry with a tolerance of 10 kilometers.

How I have to set the tolerance parameter? In which unit of measure?

I have done some try but I have not understood.

PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>
PREFIX gis: <http://www.opengis.net/ont/geosparql#>
SELECT * WHERE{

?layer <http://www.disit.org/km4city/schema#hasGeometry> ?geo.
?geo gis:asWKT ?wkt.

FILTER ( bif:st_within(bif:st_point(11.3049,43.781),?wkt, _tolerance_)=1).
FILTER ( bif:st_within(bif:st_point(11.3068,43.7811),?wkt,_tolerance_)=1).

}

Can you help me?

============

In particular, this is the ?wkt value that contains a POLYGON:

POLYGON ((11.22497476017258 43.820997211527605,11.227855048015385 43.819280760203,11.230807109337618 43.818392426222189,11.235875123265659 43.816090958559798,11.23924762920907 43.814182638800816,11.242662138451175 43.813026587465771,11.245326900138103 43.812495868235494,11.247648496494525 43.812185582495815,11.249506578105764 43.811884377017648,11.249217580931605 43.809902954361533,11.248789172799501 43.808124393011184,11.24926338931256 43.806770387513787,11.248546824793486 43.805411560104204,11.2488139834041 43.80440815688447,11.248599092442005 43.802625780820769,11.249400998846109 43.801645227927274,11.249461649208071 43.800953780070003,11.248666412115918 43.800358737011152,11.24709574723218 43.799320918907561,11.245766783204953 43.797606560197842,11.244762499872069 43.796305152804628,11.24458852059764 43.795036282743773,11.24544351072803 43.794978768929553,11.245191752256298 43.793884459429698,11.246008354866474 43.793552881440256,11.248290771890389 43.793091366204585,11.250448902462045 43.792814087970527,11.253178870525684 43.791426923082973,11.255730665170912 43.789788752996849,11.257401407070263 43.788636139680122,11.26135811091982 43.788120225534065,11.264043300459814 43.788313769250514,11.265785850883876 43.788694091306198,11.267229800343951 43.789723990070613,11.268168579878052 43.792127131483049,11.271434846578536 43.796314364572197,11.271498346308713 43.796312722128384,11.274340898929694 43.799722185915968,11.276702132274876 43.802736872056691,11.277569305273367 43.80373741627141,11.278848570876129 43.803956063871944,11.27884908715021 43.803838717178373,11.278968011067537 43.803781963608813,11.279379201503758 43.803679583702049,11.279420309692876 43.803534706713158,11.279401061577039 43.803453518536649,11.279334317483606 43.803234803264878,11.279479326527568 43.802961803605506,11.279786707717246 43.802842424062085,11.279277140443176 43.799866142940921,11.278421519553591 43.799168693764877,11.277048262182273 43.797791467939703,11.275993274720097 43.795542730049526,11.277403711218422 43.794080663092053,11.276123895444055 43.792111467141709,11.275659640384678 43.789715173836875,11.275634228533717 43.788675457089724,11.275859142791838 43.787938138836665,11.275103051148433 43.787307958993786,11.274227490281277 43.786036750989879,11.273674117123331 43.785152073485321,11.274317345429463 43.784701603378124,11.27553544327696 43.784405041268585,11.277322562984841 43.784519600594273,11.279906826083145 43.785608030435775,11.28424394163196 43.787189500789815,11.285259994758389 43.787212443292667,11.287243927591582 43.78620797407654,11.290116264373557 43.78522139790546,11.291473113903418 43.78496950047208,11.293184205764964 43.785260874301912,11.294153999395506 43.785198776546139,11.294329102999722 43.785441454439407,11.294793540708772 43.7854626616095,11.295101244473557 43.78505952671334,11.295332523938987 43.78449507349832,11.29592528591898 43.783831751268941,11.296634622930563 43.783278043977106,11.297193037072793 43.782818971736624,11.297354088550685 43.782622345490346,11.29820767228304 43.782167510817629,11.299301666189274 43.781689837224377,11.299563628219605 43.781576522130365,11.300202571002128 43.781435239273385,11.301201964352508 43.781486361994524,11.302273871097041 43.78123066543607,11.303620188231712 43.781105132017821,11.306175875523456 43.780874911636182,11.308063427886015 43.779943490308632,11.309326591613273 43.778167087999698,11.311043627623471 43.776585326773663,11.3125728215244 43.775385779112916,11.315318161531234 43.773943767071707,11.318235199165137 43.772571868140737,11.322195412834228 43.771094000141638,11.323288048066944 43.769934827239602,11.326655781950061 43.769489695902642,11.329604589037249 43.769470319265857,11.330342354675265 43.769092212733277,11.329279840671077 43.768676265711264,11.328033281882176 43.76818337251013,11.326315267270322 43.767092917318301,11.324368923074694 43.765696457402491,11.323314672040915 43.764961598287101,11.322180308655309 43.764277877345116,11.321590335211182 43.763979242790107,11.319343479751002 43.763091562729215,11.319436871471272 43.762921062484558,11.319837283806782 43.762466060560016,11.320922416627111 43.761728429058294,11.321443887341252 43.761651581413588,11.321503287690726 43.761553861938971,11.320471037815844 43.760874200035829,11.320354922687349 43.760767031235041,11.320212748207732 43.760635810178044,11.319964279170797 43.760406481867697,11.31988557452307 43.760252375274142,11.319725605874117 43.759816009909031,11.319606376262426 43.75967910085042,11.319103859080034 43.759231847638127,11.318439436550985 43.758827761867352,11.317852851155175 43.758631860821104,11.317634841100631 43.758625875667335,11.317535180884439 43.758707952410589,11.3172131277672 43.759308616627536,11.316981570949171 43.759482301045331,11.316049598850725 43.759345656007341,11.315932144293356 43.759395095399832,11.315337987836555 43.759435125931766,11.314692441928136 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43.756512890334051,11.306699533602558 43.75613708418161,11.30644073285819 43.755624601210251,11.306446726579486 43.755492847447201,11.306192707601546 43.754959198880179,11.306031689549446 43.754337238050582,11.30591327887033 43.753944909514672,11.305793697608765 43.752603443571203,11.305718435476726 43.751956702170894,11.305935821125921 43.75076383791788,11.305972365387202 43.750696653695293,11.30610478160796 43.75053533745708,11.306172547420712 43.750165361638807,11.306247311273946 43.749683503356188,11.30596075200839 43.749411607816796,11.305442662507065 43.749269605187372,11.303733486764443 43.749637022938948,11.300373675509571 43.749257432686484,11.299582992353397 43.748930318948581,11.298107226130817 43.748493109372227,11.296473822652796 43.748745110391987,11.295139614881968 43.748571818584885,11.29343948348677 43.74855775545975,11.28975895249549 43.749346782494172,11.287514168608563 43.750355961881553,11.286175603219398 43.750171301340103,11.284774174938143 43.750304149516772,11.284053385677851 43.751052265378028,11.283019146993775 43.751854283509559,11.281123907010928 43.752968714208457,11.280283283803202 43.753678701909543,11.279507705229975 43.756621371249942,11.279349439665669 43.75749068033435,11.27958332977812 43.757937670577768,11.279882013199877 43.758273311857621,11.28026128749543 43.758394379320805,11.280719382734709 43.758513872128695,11.281326894971215 43.758673258524098,11.282706705330362 43.758917264761948,11.281792708887513 43.7595143856107,11.281263736136653 43.759865120280558,11.280833392836946 43.760216742182976,11.280126622459736 43.760512519581589,11.279708563429496 43.76097527709954,11.279248151712508 43.761851090297142,11.278859936743862 43.76218757135068,11.278545542933937 43.762217663262433,11.278211095926391 43.762048529716367,11.277823399972986 43.761706083158892,11.27774678501032 43.76131407879182,11.277578061357278 43.760873766182847,11.276605685853429 43.761125405819897,11.275143209699493 43.761714343819094,11.273990846960226 43.761987411309583,11.272524492474219 43.762127864000341,11.272021304052066 43.762228481759749,11.27186681995147 43.762532300609784,11.27147422509619 43.762860700930105,11.270123173264048 43.763575800822856,11.268839147595299 43.764062848400144,11.267718146730818 43.76440669439814,11.267356173214919 43.764613383671467,11.266365599797679 43.764668769583054,11.26542865527861 43.764550148324211,11.265286451032834 43.764380490845177,11.264344466101042 43.764351520466455,11.26424649895362 43.764433859679301,11.263137707117718 43.764339698031449,11.262200569392324 43.76422128316932,11.261368245485233 43.764202027665,11.261463334742611 43.763940202550579,11.261775686874017 43.763827232105889,11.261374490742172 43.76371356248697,11.261194939099534 43.763964264610884,11.261358533637837 43.764053335265359,11.261287366337649 43.764236383052811,11.260200640462132 43.764618782445147,11.259173179848005 43.764567638712386,11.258474411398826 43.764609496920201,11.257461397688616 43.764846595540916,11.255689363574893 43.766042076845729,11.254046234679462 43.767010609779838,11.252193521846909 43.767130521197544,11.249573972240087 43.765759529000263,11.248509008767099 43.765297368215819,11.246946460483672 43.764060348628725,11.246714633065725 43.763135867017908,11.244094037471116 43.76205584451553,11.242863591566625 43.761120449472777,11.242699419947073 43.760364997282693,11.242127115398544 43.760146309342282,11.241614933922097 43.760072983641962,11.241226593480761 43.76023544213664,11.240485433065089 43.761071822303904,11.240290641243261 43.76245729254282,11.239987976532424 43.76359475075305,11.239507914100191 43.764069066870199,11.238439736128361 43.764825700104787,11.238444179671403 43.765385419530674,11.238508327903599 43.766512850929558,11.235991764742458 43.768313011926296,11.23470266559651 43.769104488511047,11.233696180626369 43.769273657497564,11.233463191446095 43.769726057192877,11.233053687103126 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43.755134387856955,11.20008163728424 43.755898810383023,11.199466897387802 43.756302303444713,11.199404188646113 43.756329981205802,11.198720947966162 43.756884789356604,11.198666570813192 43.756983975343807,11.199911434824914 43.757437207575265,11.200538410767534 43.757767272877011,11.200674792157184 43.757973710717053,11.200830798067239 43.758247837880091,11.201772733549905 43.758738396684222,11.202092567620475 43.75879165724055,11.202461909078469 43.758819652826617,11.20324669101281 43.759139998565971,11.203099907273398 43.759280044157428,11.202092545847123 43.759647903191158,11.200962857351572 43.759976332838292,11.200640751140938 43.760074734069342,11.200444197828991 43.760114533933425,11.200283504200403 43.760261686530264,11.200242666554574 43.760310012083856,11.20039674876557 43.760619651089499,11.200598804965637 43.760899374251913,11.200524466974791 43.76105386764241,11.199752590434102 43.761536918981648,11.199278566424638 43.761717292813543,11.198890040840961 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Answer 1

ST_Within tells you if a geometry is inside or touching another. So if you want to know if a point is within 10 km of another point then the point could be buffered to 10 km (or if you have a polygon, etc, you could find its center and then buffer that) in order to use ST_Within for your purpose.

ST_DWithin is probably what you are after though because it not only includes a distance parameter but also takes advantage of indices, making it much faster.

Answer 2

_tolerance_ is tacitly expressed in the unit of the requested data. So you need to be aware of the different units in which your data are expressed and be sure that you do not compare different unit systems or CRS projected data.

By default, _tolerance_ is 0.

This response concerns Virtuoso built-ins specifically.