diff --git a/include/gnss/factor/factor_gnss_fix_2D.h b/include/gnss/factor/factor_gnss_fix_2D.h
index 773a84d8bdc26cc02c62f3268b71503a9f0aa5f5..5b5e6997336abb6ae54f6d81b1fa11399420d395 100644
--- a/include/gnss/factor/factor_gnss_fix_2D.h
+++ b/include/gnss/factor/factor_gnss_fix_2D.h
@@ -42,6 +42,11 @@ class FactorGnssFix2D : public FactorAutodiff<FactorGnssFix2D, 3, 2, 1, 3, 3, 1,
 
         virtual ~FactorGnssFix2D() = default;
 
+        virtual std::string getTopology() const override
+        {
+            return std::string("ABS");
+        }
+
         template<typename T>
         bool operator ()(const T* const _x,
                          const T* const _o,
diff --git a/include/gnss/factor/factor_gnss_fix_3D.h b/include/gnss/factor/factor_gnss_fix_3D.h
index c620ee58a664234dfe4f42de64ab7bab09dc94d5..7182831792ee17803e2be80de487938a6557015f 100644
--- a/include/gnss/factor/factor_gnss_fix_3D.h
+++ b/include/gnss/factor/factor_gnss_fix_3D.h
@@ -41,6 +41,11 @@ class FactorGnssFix3D : public FactorAutodiff<FactorGnssFix3D, 3, 3, 4, 3, 3, 1,
 
         virtual ~FactorGnssFix3D() = default;
 
+        virtual std::string getTopology() const override
+        {
+            return std::string("ABS");
+        }
+
         template<typename T>
         bool operator ()(const T* const _x,
                          const T* const _o,
diff --git a/include/gnss/factor/factor_gnss_single_diff_2D.h b/include/gnss/factor/factor_gnss_single_diff_2D.h
index 3cadfcb2413f6d94429cbd04c94cb94bad90d353..8f1ca7865f0c73782f01d9fe34eb9a2f4794be9c 100644
--- a/include/gnss/factor/factor_gnss_single_diff_2D.h
+++ b/include/gnss/factor/factor_gnss_single_diff_2D.h
@@ -43,6 +43,11 @@ class FactorGnssSingleDiff2D : public FactorAutodiff<FactorGnssSingleDiff2D, 3,
 
         virtual ~FactorGnssSingleDiff2D() = default;
 
+        virtual std::string getTopology() const override
+        {
+            return std::string("MOTION");
+        }
+
         template<typename T>
         bool operator ()(const T* const _x1,
                          const T* const _o1,