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annotate pkg/models/reproject.go @ 762:01ba06da8f46

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Factored repojection of coordinates to own logic as we need it to reproject the results of the cross sections back to WGS84.
author Sascha L. Teichmann <sascha.teichmann@intevation.de>
date Tue, 25 Sep 2018 10:35:17 +0200
parents
children a244b18cb916
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01ba06da8f46 Factored repojection of coordinates to own logic as we need it to reproject the
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1 package models
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2
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3 import (
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4 "context"
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5 "database/sql"
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6 )
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7
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8 const reprojectSQL = `
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9 SELECT ST_X(p), ST_Y(p)
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10 FROM ST_Transform(ST_SetSRID(ST_MakePoint($1, $2), $3::integer), $4::integer) AS p`
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11
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12 type Reprojector struct {
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13 stmt *sql.Stmt
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14 FromEPSG uint32
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15 ToEPSG uint32
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16 }
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17
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18 func NewReprojector(
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19 conn *sql.Conn,
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20 ctx context.Context,
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21 fromEPSG, toEPSG uint32,
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22 ) (*Reprojector, error) {
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23 stmt, err := conn.PrepareContext(ctx, reprojectSQL)
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24 if err != nil {
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25 return nil, err
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26 }
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27 return &Reprojector{
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28 stmt: stmt,
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29 FromEPSG: fromEPSG,
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30 ToEPSG: toEPSG,
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31 }, nil
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32 }
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33
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34 func (r *Reprojector) Close() error {
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35 if s := r.stmt; s != nil {
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36 r.stmt = nil
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37 return s.Close()
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38 }
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39 return nil
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40 }
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41
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42 func (r *Reprojector) Reproject(
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43 x, y float64,
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44 ctx context.Context,
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45 ) (v, w float64, err error) {
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46 err = r.stmt.QueryRowContext(ctx, x, y, r.FromEPSG, r.ToEPSG).Scan(&v, &w)
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47 return
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48 }