Fix Readme bug.

Replace the SGP4 library

entity/gp.go

@@ -1,8 +1,8 @@
 package entity
 
 import (
-	"github.com/SharkEzz/sgp4"
-	"strings"
+	"github.com/shibingli/spacetrack/internal/satellite"
+	"time"
 )
 
 type GP struct {
@@ -48,32 +48,6 @@ type GP struct {
 	TLELine2           string `json:"TLE_LINE2,omitempty" xml:"TLE_LINE2,omitempty" bson:"tle_line_2,omitempty"`
 }
 
-func (g *GP) TLE() (*sgp4.TLE, error) {
-	name := g.TLELine0
-	names := strings.Fields(name)
-
-	if len(names) > 1 {
-		name = strings.Join(names[1:], " ")
-	}
-
-	tle, err := sgp4.NewTLE(name, g.TLELine1, g.TLELine2)
-	if err != nil {
-		return nil, err
-	}
-
-	return tle, nil
-}
-
-func (g *GP) SGP4() (*sgp4.SGP4, error) {
-	tle, err := g.TLE()
-	if err != nil {
-		return nil, err
-	}
-
-	sgp, err := sgp4.NewSGP4(tle)
-	if err != nil {
-		return nil, err
-	}
-
-	return sgp, nil
+func (g *GP) SGP4Position(utcTime time.Time) *satellite.LLA {
+	return satellite.LatLonAlt(g.TLELine1, g.TLELine2, utcTime)
 }

go.mod

@@ -2,4 +2,5 @@ module github.com/shibingli/spacetrack
 
 go 1.18
 
-require github.com/SharkEzz/sgp4 v1.0.1
+require github.com/joshuaferrara/go-satellite v0.0.0-20220611180459-512638c64e5b
+require github.com/pkg/errors v0.9.1 // indirect

go.sum

@@ -1,2 +1,10 @@
-github.com/SharkEzz/sgp4 v1.0.1 h1:Ws8mAUpvSzZ3ocbacb9FaWoqDYh5wj6xIjHARhXXVzY=
-github.com/SharkEzz/sgp4 v1.0.1/go.mod h1:Ij16kwC0HZob8vkFmHb5YjVyu2BmyUflL0RFpNim0dQ=
+github.com/joshuaferrara/go-satellite v0.0.0-20220611180459-512638c64e5b h1:JlltDRgni6FuoFwluvoZCrE6cmpojccO4WsqeYlFJLE=
+github.com/joshuaferrara/go-satellite v0.0.0-20220611180459-512638c64e5b/go.mod h1:msW2QeN9IsnRyvuK8OBAzBwn6DHwXpiAiqBk8dbLfrU=
+github.com/onsi/ginkgo v1.2.1-0.20160509182050-5437a97bf824 h1:MbMqwlWoESqhGm4Sslfdyeq7Ww8R9ppeKS5DcO3xDI0=
+github.com/onsi/ginkgo v1.2.1-0.20160509182050-5437a97bf824/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
+github.com/onsi/gomega v0.0.0-20160516222431-c73e51675ad2 h1:38zSYUaJJkzreBjLz7tx4AUTVjnFI7EQBnlRoWt4QFA=
+github.com/onsi/gomega v0.0.0-20160516222431-c73e51675ad2/go.mod h1:C1qb7wdrVGGVU+Z6iS04AVkA3Q65CEZX59MT0QO5uiA=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+gopkg.in/yaml.v2 v2.0.0-20160301204022-a83829b6f129 h1:RBgb9aPUbZ9nu66ecQNIBNsA7j3mB5h8PNDIfhPjaJg=
+gopkg.in/yaml.v2 v2.0.0-20160301204022-a83829b6f129/go.mod h1:JAlM8MvJe8wmxCU4Bli9HhUf9+ttbYbLASfIpnQbh74=

internal/satellite/satellite.go

@@ -0,0 +1,58 @@
+package satellite
+
+import (
+	goSatellite "github.com/joshuaferrara/go-satellite"
+	"time"
+)
+
+func ParseTLE(line1, line2 string) (sat goSatellite.Satellite) {
+	return goSatellite.TLEToSat(line1, line2, goSatellite.GravityWGS84)
+}
+
+func Propagate(sat goSatellite.Satellite, t time.Time) (position, velocity goSatellite.Vector3) {
+	return goSatellite.Propagate(sat, t.Year(), int(t.Month()), t.Day(), t.Hour(), t.Minute(), t.Second())
+}
+
+func TLEPropagate(line1, line2 string, t time.Time) (position, velocity goSatellite.Vector3) {
+	tle := ParseTLE(line1, line2)
+	return Propagate(tle, t)
+}
+
+func ECIToECEF(eciCoords goSatellite.Vector3, t time.Time) (ecfCoords goSatellite.Vector3) {
+	return goSatellite.ECIToECEF(eciCoords, GSTimeFromDate(t))
+}
+
+func ECIToLLA(eciCoords goSatellite.Vector3, t time.Time) (altitude, velocity float64, ret goSatellite.LatLong) {
+	return goSatellite.ECIToLLA(eciCoords, GSTimeFromDate(t))
+}
+
+func LatLongDeg(rat goSatellite.LatLong) (deg goSatellite.LatLong) {
+	return goSatellite.LatLongDeg(rat)
+}
+
+type LLA struct {
+	Latitude  float64
+	Longitude float64
+	Altitude  float64
+}
+
+func LatLonAlt(line1, line2 string, t time.Time) (deg *LLA) {
+
+	pos, _ := TLEPropagate(line1, line2, t)
+
+	alt, _, ret := ECIToLLA(pos, t)
+
+	latLong := LatLongDeg(ret)
+
+	lla := &LLA{
+		Latitude:  latLong.Latitude,
+		Longitude: latLong.Longitude,
+		Altitude:  alt,
+	}
+
+	return lla
+}
+
+func GSTimeFromDate(t time.Time) float64 {
+	return goSatellite.GSTimeFromDate(t.Year(), int(t.Month()), t.Day(), t.Hour(), t.Minute(), t.Second())
+}